You didn't mention a budget.
I'm in a similar situation, I think. My band practices in my basement and my neighbors have a baby. We have two electric guitars, bass, singer, drum kit. Sometimes we play pretty loud!
My approach was to use DIY panels of 2" Roxul Rockboard 80, spaced (where possible) 2" from the wall. I didn't bother with bass traps, maybe someday I will, but currently have too many projects.
I made 2 x 4 frames to support the Roxul. The finished panels are light, maybe 8 lbs apiece, and hang on the walls with picture wire and hooks, so nothing is permanently attached.
Lot's of information on this site where i bought the stuff:
Depending on your budget, you could also use some of the other Roxul products, some available at one of the big box home improvement stores.
Mine is a relatively small room (maybe 10x12), so I just covered as much of the walls as possible. It's pretty effective. I do some recording, everyone close mic'd with the full band playing works pretty well.
End result ? When I asked the neighbors if the band was too loud, and the answer I got was "oh, you have a band?"
Have fun.
-Bob