That little plastic tab on new cranks is a good place to start: 2-3 mm clearance and dead parallel. Otherwise just use the eyecrometer. Some derailleur outer cage plates have an angle - in that case usually the longer rear section is the part to align. When you're using compatible parts, that should be all you need to get it working smoothly. With a mix of parts you may need to angle the cage, for example if the chain refuses to climb onto the big ring, but slackening the top limit throws it off the outside, then turning the cage slightly nose-in may help. It can also help to bend the front of the inner plate slightly outwards to give the chain an extra nudge as it climbs. But these are not normal adjustments so much as hacks - modern front mechs and chainsets have features that should make this sort of tweaking unnecessary.