Some more tips some have prob already been mentioned though...

Dont hold your hand under the belly when getting a photo with a fish, it sags up and looks crap!!

Hold you fish so that 100% of the side is visable, in other words dont let it roll back so you can mainly see its date..

Blood is the worse pic wrecker...

Watch out for hat shade!

Also if the sun is behind you either move around or spin the boat.

And look happy!! smile!

Having a decent camera helps too. I use a Canon dslr and love it! However i even had a photo printed ont he front page of Fishing world that i took with my old cheap 6 mp Fuji!!