I hope you have been working on some of the suggested songs for various lessons. Playing real music is essential. Just make sure you are paying attention to what you are playing. Don't just memorize a sequence of notes or finger motions. You're not training to be a robot.
Know what key you're in. Know the chord the notes relate to. Study the rhythms used.
The more details you notice, the more influential they will be on your playing.
At this point many things will be mysterious to you. As we move ahead many of these little mysteries will be solved.
Easy Basslines to Learn
I've assembled a list of 80 or so easy basslines which apply many of the concepts we've discussed so far. The sheet music for these songs can be found in the recommended books (or links next to the songs).
The things I ask you about each song are the types of questions I want you to ask yourself as you learn songs and basslines. Just passively memorizing where to put your fingers isn't enough. Use your ears. Use your mind. Study!
The Whole Thing
Also, play the whole song, not just the main riff.
Always learn each song from start to finish just like you would have to perform it.
Play Songs Like in the Real World
Make sure you don't only play songs along with the recording. Play to a metronome. Then, play it without a metronome. Record yourself.
When you play along with recordings, you lean on them. Recordings give you all sorts of cues like when to change parts, what the rhythms are, and where the beat is. These are all things you need to internalize. These are your responsibilities in a band.
Take off the training wheels!