Getting your shots leveled for architecture,.. aargh

this and the the "Free Transform Tool" (and basic lens correction) and you should be able to climb out of most geometry problems - but also I agree with Reilly, the little spirit level that goes into your flash foot does the trick for me most of the time

But also you need to become more aware of  "One Point Perspective" or more specifically you need to learn that if you are close to OPP, you need to nail it OR you should be sufficiently off "One Point" so that it is obvious ... generally speaking, there is a de facto "no man's land" of close-but-not-quite one point that you should avoid in architectural photography ...