Like Phalex and mothmonsterman, I don't do anything special to my solidbody basses or guitars...they are pretty hardy, like moth says.
Watch out for rapid, large swings in humidity or temperature. For example, if you know the humidity in your house is going to jump or drop 30-40% in one hour, you might want to keep the bass in the case with a little humidifier until the humidity settles down. This situation is pretty rare in most modern houses though and even if it did happen to your bass it would probably only change the relief in the neck a little.
Of course, leaving a humidifier in with the bass never hurts...
You probably already know this, but also avoid leaving the bass in a hot or cold car for more than about ten or twenty minutes at a time.