[the embezzler]

Lots of good ideas mentioned here already so 'll be brief....

I play part-time in a soul covers band with horns and am one of 2 guitar players.
We both play Tele's.
We haven't really discussed it a whole lot but what seems to happen is one of us will either know the song in question better than the other one, or one of us kind of just takes charge on the main guitar part straight away.
Then the other guy will just play around that main part; that could mean doubling the bassline, doubling the riff in harmony a third up (which can be super cool if done sparsely and with taste) or maybe playing some stabby, complimentary chord part.
Tremolo and reverb can be very handy for defining parts in a twin guitar attack.

You just have to be mindful of not getting in the other guys way too much.

Hope this helps.