This fast guitar lesson is going to let you know what it takes to learn a song, and no, it's not going to take months to do it either. The reason that beginning players are coerced to learn practice scales and riffs is because this helps to establish a strong foundation to play almost anything later.
However, if you just wanted to dive right into songs, there's a straight-forward method to focus on your skills on just that song and it's simple to learn. So, let's take a look at 6 things you need to know to learn a new song or tune.

1. How many chords are used and what are they? The odds are that any song that you're attempting to play is based on a simple set of chords and that's what you need to know first. So, get onto the web and type "Your song name's chords" and I'm sure you come up with a long list of results. Try to stick with songs that have four chords at the very most if you're just beginning.
2. What is the song's tempo? Is this going to be a fast or slow tune? For beginners, it's best to start with something slow or at an average tempo of around 120bpm which is considered andante. Any fast guitar lesson will tell you that it's a good idea to use a metronome when you're practicing to keep up with a tempo as well.
3. Does it match my skill level? This step is sort of reiterating what has already been said, but by this point, you need to realize if the song you're going for is too difficult. If it is, don't be discouraged. You'll get to that point eventually, but for now you should try something easier to keep your motivation going.
4. What are the chord progressions and transitions? In this fast guitar lesson I'd like to stress the importance of smooth transitions in a guitar progression. Learn what order the chords come in and how they transition, but as you practice those transitions, make sure that everything is flowing together smoothly. The smoother your transitions, the more you'll be recognized as a professional player.
5. What is the rhythm of the song? Now that you have the chords and tempo down, it's time to tackle the rhythm. This is more about what variations of strumming patterns are used through each chord. Try to sync up as close to the recording of the song as you can to make your playing authentic.
6. What defines the song? This is more a subjective section to this fast guitar lesson, but it's about knowing what to add into the song besides just the base chords. Maybe there's a specific intro riff or lead section that really identifies the tune. Think about what creates the originality of the piece and that's the last thing to learn.

from goarticles.com

Core Members: Kurt Cobain, Krist Novoselic, Dave Grohl
Formed in: 1987, Aberdeen, Washington
Key Albums: Nevermind (1991), In Utero (1993)
Nirvana are one of the most well-known and successful rock groups in the history of recorded music. The trio from Seattle were fronted by Kurt Cobain (born February 20, 1967, died April 5, 1994), and featured future Foo Fighters frontman Dave Grohl on drums. Their second and third albums, 1991's Nevermind and 1993's In Utero, are two of the biggest selling records in history. With their legacy preserved by the shotgun suicide of Cobain in 1994, Nirvana retains the air of legend.
Background
Nirvana were born in Aberdeen, Washington, in 1985, when Cobain and bassist Krist Novoselic were introduced by their mutual friend, Buzz Osborne, of The Melvins. Osborne had been instrumental in Cobain's musical growth, taking along the 14-year-old Kurt to his first-ever rockshow: Black Flag. Growing up in the "redneck, backwoods" logging town, Cobain was an intense loner who sought refuge in records.
"I was so antisocial that I was almost insane," said Cobain, of his teenage years, in a 1993 interview with Howl. "I felt so different and so crazy that people just left me alone. I wouldn't have been surprised if they had voted me Most Likely To Kill Everyone At A High School Dance." Fittingly enough, Cobain's early songs —inspired by '80s hardcore bands like Scratch Acid, Rapeman, Flipper, and Black Flag— were, by his own admission, "really angry." Beginnings
Playing gigs around Aberdeen and Olympia, the budding Nirvana developed a strong local following. Recording demos with Jack Endino, the band caught the attention of nascent Seattle label Sub Pop. They agreed to put out Nirvana's debut album. The $606.17 it cost to record such —cemented in legend on the liner-notes— was donated by Dylan Carlson, a friend of the band who was listed as having played 'guitar' on the recordings, but was really more a patron. Grohl, such a signature part of Nirvana, didn't arrive until the next album.
Bleach, the finished record, was released in 1989; its raucous garage-rock topped off with lyrics about "life in Aberdeen." Playing on the role of outsider, Cobain's lyrics immediately struck a chord with disenfranchised youth in the US and Europe. Whilst Bleach's initial sales of 35,000 copies seem scant compared to later Nirvana albums, it represented an underground breakthrough. Championed by bands like Sonic Youth and Dinosaur Jr., and receiving intense critical acclaim, Nirvana were courted by major labels. At the recommendation of Sonic Youth's Kim Gordon, they signed with David Geffen's DGC.



Breakthrough
In 1991, Nirvana became the biggest band in the world. Essentially on the back of one song: "Smells Like Teen Spirit." With its title taken from a piece of graffiti spray-painted by Bikini Kill's Kathleen Hanna, the song was Cobain's attempt to "rip off The Pixies." When the band first played it to Butch Vig, the producer in charge of their second album, he could barely contain his excitement. "It was awesome sounding," Vig would tell Rolling Stone. "I was pacing around the room, trying not to jump up and down in ecstasy."
The cut was a monstrous hit, setting the table for the incredible success of record number two, Nevermind. Geffen, proving they had no idea what they were onto, initially only pressed 400,000 copies. It has ended up selling over 26 million copies. Of course, its growth was slow; having debuted only at #144 in the US.
Though others could see the writing on the wall (the Village Voice called Nevermind "the catchiest, chock-full-o-anthems record since [Bon Jovi's] Slippery When Wet"), Cobain remained defiant. "I'm not into ambition or salesmanship," Cobain said, at the time. "I don't see Nirvana getting as big as Metallica or Guns n' Roses," he'd later offer, even after his band was on its way to Gold Status.
In some ways, this foreshadowed Cobain's contentious relationship with the masses. "I just can't accept that mainstream macho-dickhead attitude. I wouldn't be comfortable having that many people in my audience every night that are like that," he lamented. Speaking to Shark zine in 1991, he burned with resentment, saying he was "disgusted" at "how spineless, lethargic, and guilty" Generation X was. If this was Cobain being spokesperson for a generation, he wasn't pulling any punches.

Contention
In 1992, to capitalize on Nirvana's astonishing success, Geffen cobbled together a collection of unreleased tracks, demos, rarities, and alternate versions. Cobain, ever the provocateur, called it Incesticide. The frontman seized the opportunity to write a withering broadside in the liner-notes that proved so controversial it was omitted from later pressings. "At this point, I have a request for our fans," Cobain wrote, in his 'open letter.' "If any of you in any way hate homosexuals, people of different colour, or women, please do us this one favour for us - leave us the fuck alone! Don't come to our shows, and don't buy our records."
Cobain's vocalized frustrations came at the culmination of a year in which the band, having grown into a corporate behemoth, had to deal with criticism from their initial audience: punk-rock fans. As someone who loved nothing more than "pure underground music" —his favorite bands at the time included The Vaselines, The Raincoats, Os Mutantes, and Young Marble Giants— it hit Cobain where it hurt. "I felt terrible," he told Sassy, "to be shunned by this claim that just because you are playing the corporate game you are not honest."
"I don’t blame the average seventeen-year-old punk-rock kid for calling me a sellout," Cobain said, in a '92 interview with Rolling Stone. "I understand that. Maybe when they grow up a little bit, they’ll realize there’s more things to life than living out your rock n' roll identity so righteously."
In February of 1992, Cobain had married his girlfriend, Courtney Love of the band Hole. In August of that year, their daughter, Frances Bean Cobain, was born. In an interview with The Los Angeles Times in 1992, Cobain credited that union with helping keep him off the edge. "I guess I must have quit the band about 10 different times in the last year," he said. "I'd tell my manager or the band, but most of the time I would just stand up and say to Courtney, 'OK, this is it.' But it would blow over in a day or two."
Cobain lamented that "the biggest thing that affected [him] was all the insane rumors, the heroin rumors," yet, both he and Love had gone on the record confessing to using the drug. "To escape from it all I did heroin for quite some time," Cobain told Dutch magazine OOR.

Legacy Cemented
Out of that dark period came In Utero, one of the bleakest albums ever to debut at #1 worldwide. Having wanted to "record a really raw album for almost a year," Nirvana hooked up with producer Steve Albini, the former Big Black and Rapeman frontman renowned for his simple, unfettered approach to production. Said Cobain, to OOR, of the album: "the image of the group had been hyped up to outrageous proportions, we had the idea it didn't matter what we recorded: it would sell anyway."
The results didn't go down well with Nirvana's vested corporate overseers. "My A&R man called me up one night and said, ‘I don’t like the record, it sounds like crap, there’s way too much effect on the drums, you can’t hear the vocals.’ He didn’t think the songwriting was up to par," Cobain told Melody Maker. "A few other people —our management, our lawyers— didn’t like the record either."
Though Cobain felt like he didn't make "negative record" —lead single "Heart-Shaped Box"'s chorus of "Hey/Wait/I’ve got a new complaint" was him joking about his portrayal in the media— in Utero is clearly the chronicle of a troubled soul.
If Nevermind's leadoff song, "Smells Like Teen Spirit," set the tone for that album, so, too, did In Utero's opening track "Serve The Servants." Though Cobain claimed the album was "about disease, bad health and the feeling of being trapped," it plays like a meditation on self-loathing. Its sardonic, cynical, ironic opening lines —"Teenage angst had paid off well/Now I'm bored and old"— set the tenor for the record, which Cobain initially wanted to call I Hate Myself And I Want To Die.

Things Fall Apart
At the time, that shelved working-title seemed like comedy, but less than a year later, it seemed like a sad cry-for-help. After Nirvana had played their legendary MTV Unplugged set in November of 1993 —later enshrined on both album and video— Cobain tripped into a downward spiral of drug-abuse and sickness.
After one heroin overdose, and another on Rohypnol and alcohol, all of Nirvana's immediate tour-dates were cancelled. Cobain, at the behest of his wife and friends, checked into a rehab center in Los Angeles. After only one day, Cobain climbed a fence, took a taxi to LAX, and flew back to Seattle. His whereabouts unknown by family and friends, Cobain committed suicide in his Lake Washington home on April 5, 1994, although his body was not located until three days later.

"I haven't felt the excitement of listening to [and] creating music," his suicide note read, in part, "for too many years now." Seemingly thinking about the power and integrity of his music until the very end, Cobain's legacy as devoted genius was sealed.