Watching the BBC Young Musician competition on TV recently, it was great to see so many outstanding musicians play. From piano to percussion, cello to bassoon it was obvious that these performers were dedicated to their art.
Looking into the individual's backgrounds a little more, there was an average of 2 hours each day scheduled for their practice. This did vary though - the keyboard finalist, pianist Yuanfan Yang (15 years old) practiced 3 hours a day while the overall winner, cellist Laura Van Der Heijden (15 years old) opted for 4 hours (plus one hour for piano!).
Many hours of practice may seem far removed from you, especially if you've a demanding job and a busy family life. That said, it's not a black and white choice of 2 hours+ or nothing, that's way too defeatist an attitude to have. Instead, plan on setting up small slots in your day and applying a time hierarchy - work and family commitments come first, but the guitar comes above other hobbies or elongated bouts of TV watching and/or web surfing.
It's logical - you're fitting your musical desires into what you can realistically manage. Now try the following schedule that works for some time starved guitarists I know: 20 minutes before work (technique warmup), 15 minutes at lunch (tricky sections in repertoire), then 45 minutes at night (30 minutes repertoire practice, 15 minutes improvising over backing tracks). That's nearly an hour and a half each day sorted with a varied agenda and enough to start producing noticeable results after the second or third week.
You may not have 4 hours a day available like these 15 year olds but don't dismiss several short practice segments each day as not worthy because they are. Of course, you now need to decide on how to personalise these slots.
Aim for balance in the areas of technique development (eg improve your picking), fretboard knowledge (eg Bb natural minor all over the fretboard), repertoire cultivation (either for gigs or your choice; try varying genres) and improvisation approaches (eg a 12 bar dom7 blues and the changes for My Funny Valentine). For now though, claim a 15 minute slot and try one of the short licks available on this site!