in my current band that was an exciting time, too...
we've founded the band about 9 months ago, and we didn't really know what we want to do.
we all listen to nearly the same music, which is a big plus, but still we had three different genres we liked:
stoner rock - like QOTSA
post-punk - Interpol, Editors
post-rock - Explosions in the Sky, GY!BE
the first song we wrote was a heavy, 9-minute beast of kyuss-stoner rock: dropped tuning, distorted bass, 5-minute long instrumental part with free jam sections, mantra-like repetions, and all that stuff. we had a blast.
the second song was completely different, very joy division-like, with a very high bass line, guitar with tons of delay and chorus; but still had a touch of the post-rock-genre with crescendos and a huge wall of sound in the middle part. I especially liked how guitar and bass never played the same notes and it sounded more beautiful than anything I've ev er done musically.
the third song was pretty weak, again distorded bass, but somehow sounded like a motörhead-cover of a missing ramones b-side. awful.
the forth song came out pretty impressive, it's still the longest (and slowest) song we've written to date. it's based around one simple guitar melody, which stays pretty much the same through the whole song, but bass and drums make such an atmosphere, it's very intense. every time we play it, it feels like meditation.
so, well, that was the material we had when decided to record some music that peaople can get an impression of us. but you can image, with that tracks mentioned above, it would have been a confusing impression.
so, what did we do?
we kicked song #1 and song #3 only one day before the recording session, decided #2 and #4 to be our starting points to find our sound, and never looked back.
we still had to write some more songs to define our sound (#5 went to garbage during the 2nd recording session), but now we nearly achieved it. and it's a good feeling.
so, my advice: write songs (sometimes the bad ones help more to define your style than the good ones), be honest to each others about these songs, show the others your favourite songs or stuff you'd like to do, and: be open. good luck