How Much Should I Practice?
The more you practice the better. That assumes you are practicing the right stuff. Obviously, there are other things in life such as school, work, and family that prevent you from practicing. To make progress on the bass, what is most important is frequency of practice. It is critical for you to practice some every day. Even if you only have 5 minutes, do it. It will make an impression on your mind, your ears, and your fingers.
Your typical practice routine should be at least 30 minutes a day. I think a good amount of practice for most people is about 1 hour every day. It all comes down to your goals. If you have tremendous goals for conquering the world with your bass playing, an hour a day won't cut it. You may not realize that the best players in the world spent a number of years practicing 6 to 12 hours a day! Saxophonist Charlie Parker, after being humiliated, practiced 12 hours a day for 3 years or so. He went back to the jam session where he blew it the first time and smoked them all. Jimi Hendrix never put the guitar down even when he went to the bathroom.
There is so much competition for your time, you have to sacrifice something. Watch less TV. Don't go out as much. Sleep less. Wherever you can squeeze more time out of your day, do it. If you want it badly enough, you will find the time to practice.
A little practice anecdote: After a violinist's amazing performance, a woman approached him and said, "Sir, I would give my life to play like you!" He replied, "I did."