I'm in this band and we generally just play a bunch of blues progressions or riffs with bluesy sounds to it but we can never seem to create any good lyrics to these "songs" so how would you go about writing lyrics for a blues song?
Find a problem in your everyday life and go on and on about why it's a problem.
Yeah man. It's called blues for a reason (not being a jerk or anything). Not even something that is a problem. Just write about something that is meaningful to you and only you. Something that makes you sad, angry, or any other emotion!
blues is something you have to feel, not saying that you dont have to feel other sorts of music,
but with blues what id recommend is jamming, playing music, and start singing.

it can be anything , " oh i have no more pudding"
whatever just let it flow with the music and what you are feeling,
I got up this mornin-ah!
da-na-na- na-na
And my toes were cold
da-na-na- na-na
I opened my sock drawer
da-na-na- na-na
Then I remembered, They were all down the stairs! I got the,

I got the cold feet blues!
or, you could not take that route, ditch the "poor me i had a bad day" crap and sing about the opposite!

kind of like stevie ray vaughan.

then again, if you're going traditional, votes for craigs cold feet blues, that **** sucks. *cold feet that is