I would try to figure out the rhythm guitar riffs and accent the "important" notes in that. Make sure your hits line up with the kick; for example if he's doing 16th notes maybe try and peddle 8th notes. If you have two guitarists doing some noodly harmonizing stuff just keep the low end solid with the drums. Remember "while you're up there solo'ing, who is playing the bass?" to quote the musical advice thread
I play bass in a metalcore type of band and I try to keep it simple, less is more. In past bands I did the thrashy deathmetal shredding stuff but now I much prefer to focus on my right hand and keep it super tight with the drums.
Also, I joined a band a few months ago with the same thing going on. Had a show in a month, recordings already in progress etc. I just made sure I asked a lot of questions of the guitarists. There is no wrong in asking a question about trying a couple different runs to find out what sounds the best.