I like "A" squared plus "B" squared equals "C" squared. This formula gives you the distance between marks when you need to use a pair of 45?s to miss an object preventing you from making a simple 90?. It keeps the pair of bends looking like they belong together.
So if you want to leave a wall at a 45? angle 16" from the ceiling, and hit the ceiling with a 45? 16" from the wall the conduit is leaving you whip out your cellphone and type in 16 x 16 = 256 + 256 = 512. The square root of 512 is 22.62.
So you measure where you would want a 90? (if you could), subtract 16, make a mark. Go up the conduit 22 5/8", make another mark. Bend on the notches and install.
Before I figured this out, my attempts always looked pretty bad. I couldn't make a tape measure do this for me, myself.