Open up audio for the riff and follow the tabs. Open the song that you're covering in another window on your internet browser. Play through the song and trace the chords and notes with the tab that you looked up. Try to follow the numbers on the tab with the notes that are being played in the song. Try to get an understanding for which chords the artist is playing before trying to duplicating it.
Justin Sandercoe has thought long and hard about how to teach people to play the guitar, and how to do this over the internet. He has come up with a well-designed series of courses that will take you from nowhere to proficiency. I tried to learn how to play years ago, using books, and got nowhere. I've been using Justin's site for just over a year and I feel I've made real progress. What's more, Justin offers his lessons for free - a boon for any young player who has the urge to play, but whose pockets are empty. I've seen and used other sites for learners: none of them offer as clearly marked a road as Justin does.
Okay, so if the diagram had O’s across the whole thing, then you wouldn’t even have to touch the fretboard at all, you would just strum it. However, this diagram has a couple of other marks on it, and those indicate where we need to place our fingers. In this case, they are on the 2nd fret of the 4th and 5th strings. The frets are the metal parts running perpendicular to your fretboard; they are what the string makes contact with when you press your fingers down. On the diagram, the frets are the horizontal lines. So count up to the second fret, and put your fingers down just behind the fret, like in the diagram.
You do not need long fingernails to play guitar. In fact, it's best to keep your fingernails short! As for the callouses, these may be unavoidable. If you would like to avoid them as much as possible, ask your guitar instructor about lowering the action of your guitar (the action is the distance between your strings and your frets) so that the frets are easier to press down on.

Español: tocar la guitarra, Deutsch: Gitarre spielen lernen, Português: Tocar Guitarra, Français: jouer de la guitare, Русский: играть на гитаре, 中文: 弹吉他, Čeština: Jak se naučit hrát na kytaru, Bahasa Indonesia: Bermain Gitar, हिन्दी: गिटार बजाएं, العربية: العزف على الجيتار, Tiếng Việt: Chơi Đàn Ghi ta, Italiano: Suonare la Chitarra, 日本語: ギターを弾く, ไทย: เล่นกีตาร์, Nederlands: Gitaar spelen, 한국어: 기타 치는 법, Türkçe: Gitar Nasıl Çalınır
I've seen so many guitar lessons where the instructor simply dives right in and begins teaching chords. Unfortunately, that assumes that the student's guitar is already in tune! Guitars are made out of wood, and wood reacts to our environment, be it hot, cold, dry or humid. As such, guitars frequently go out of tune, and they must be tuned to make them sound good. If you begin learning to play guitar on an out of tune guitar, it will not sound good to the ear no matter how hard you try, and as such, it will become discouraging pretty quickly.
Beginning Guitar Class - Open to all beginners age 13 and up, or intermediate players who want the review. Begins with holding and tuning your guitar, names of guitar parts, and quickly progresses to chords, scales, tabulature, and playing basic songs. A variety of styles are introduced to encourage students to explore and find the styles they like best. Classes are organized according to age and skill level, so it's an easy way to make new friends too. Classes start every month and may be repeated as often as you like. Cost is $70 per month (4 hours).