Work on stretching your fingers since frets are farther apart on bass. Also, work on your finger strength, and of course, on your fingers for plucking the strings. There really isn't much to say...u'll probably find out what you need once you start playing.
Originally Posted by evening_crow
Quoting yourself is cool.

WARNING: I kill threads.
Not really, just get a bass and learn to play it. You have an advantage over first timers in that you can already use your left hand, so its just getting callouses.
"Their fate is in each others hands as they decide whether to share... or to shaft"
Robert Kilroy-Silk from his sadly shortlived quiz-show Shafted.

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try to get used to play with your fingers, not a pick. Unless you're in to punk rock and that stuff, avoid the pick at all costs. Learn to use both your index and middle fingers and not just your index. Also, start off slow just like you did on guitar, don't assume you can automatically play stap bass and fingertap after a week. Practice makes perfect. Keep bassin!

...and you made a wise choice switching to bass, because everybody and their grandmother plays guitar...
mark ^||^
Truthfully, since you're already a guitar player, I'd definitely work on using your fingers to pluck. It's quite a lot of fun once you can do it. Although, it all depends on what sound you like better too. I use my fingers for softer songs, but I tend to pick for other songs, cuz i like the punchier sound.