| I too was recently coming back from long lay off. get a metronome, and a keyboard if you can... then
1. hatch out the Circle of 4th/5th (key sigs; Maj and Min; of you know those, learn Pentatonic or Blues scales..)
2. Pick 5-10 songs you wish to learn (or re-learn) and work on them. -what I am doing in this regard- is learning the treble melody parts too, and working out drum parts for my bass too; (dampens, mutes, dead-notes, slapNpop..mostly for rhythm studies) re-creating the song with bass essentially) do a couple songs per week (if not more)
3. If you are going to learn to read music, (or again re-learn) pretty much need daily effort. (15-30 min if you can spare it) I honestly have to get better at doing this myself. and start transcribing (and transposing) as soon as possible.
4. Pick a few techniques you wish to improve on, or solidify. (slap, tap, legatto/stacotto)
5. Train the hell outta your ear! AM/FM radio, CD, MP3, Pod Casts, You tube, iPhone/Android apps etc..
Keep a journal if you can. I find if I set a practice schedule for the week and stick to it, it works out the best. I am a cronic noodle-er so I get my "Work" out of the way first, then reward myself with mindless noise..
and finally if you find a Jam session or buddy to play some songs with.
Just because I know others will suggest it too; Get a teacher if you can afford it.. (something else I need to do aswell)
there is way more, but this will get you started...have some fun bro. | 
