Like a lot of folks out there, I started out learning bass primarily from tab sites on the internet. It was a great way to get started quickly. I did some "self-learning" stuff from books, etc. but it really didn't seem to contribute to my early playing as much as the tab sites did. After a while though I found that I could not play much of anything without going to the tab sites first - there were times when this was very detrimental of course, such as when going to jam with friends and encountering material I had never played before. Even playing over a simple three chord song was tough unless I stuck with root notes only. It also was stifling any creativity I had - even when I could "hear" a bassline in my head, I could not reproduce it on my instrument. So frustration was setting in and my desire for playing was decreasing. Lots of folks around here are really opposed to using tabs and I began to understand why. Seems tabs get you going fast, but makes developing as a player much harder than if you approached things correctly from the beginning. Now I don't rely on tabs hardly at all - even when I do reference them, I generally find much of what's out there is not correct anyway or that I've already developed a better bassline on my own. I've worked hard to get away from using those sites and it has really opened things up and improved my playing tremendously.
Thought I'd share how I did it, since for the longest time I knew I needed to do it, but had no real idea how. Here are the things that helped me - hope it might help some of you as well. For the more experienced players out there than me, I'd love your input as well, for all of our benefit.
1. Take private lessons from a good teacher (who teaches primarily bass vs "guitar and bass") - I learned some pretty important concepts through this that I could never quite grasp from the books I was reading out there. Expensive and a commitment, but worth it.
2. Get good practice aids and use them often. I use a music download service through a wireless broadband connection in my house. Let's me develop playlists, etc which I then can sit in front of the computer and learn. I can burn CDs and listen to them in the car - hearing the basslines over and over again. Works for me and I know there are other aids specifically for learning bass that allow you to slow down the songs as needed.
3. Jam with a band. Playing along with CDs in your bedroom is okay for a while, but nothing is like "real world" experience - it is good for your learning and is a blast as well. You'll encounter music you don't know. Learn to roll with it - you might fumble around for a while, but will get better.
4. Use guitar chord charts as opposed to bass tab starting out or later on if you get stuck. If you have some fundamental theory knowledge and train your ear, you can develop your own lines over the chord charts. I found this was very helpful in making the transition.
Anyway, hope these tips help out - they worked for me and I'm a better musician (though still have a LOT of learning left to do) and enjoying it much more as well.
PEACE
