Hey lots of good advise above maybe also consider doing finger exercises when not on guitar. Be careful with the commercial guitar finger squeezers as they now claim to start RSI.(repetitive strain injury)
Refer http://eeshop.unl.edu/music.html

Suggest squeeze a soft ball slowly and release that fits in your fretting hand. Keep it simple but consistant especially on first digit finger say 100 times a day move up 300 times a day incrementing 10 extra a day (i,e 100 then 110, then 120 etc) so in twenty days you can break the guitar neck with your bare hands...just kidding