What are some tips to installing cabinet doors and hinges so that they are positioned correctly and look good? I've been to some showrooms (IKEA) where the doors look slightly crooked or they don't look perfectly symmetrical or the gap between left/right cabinet doors amongst the cabinets in the kitchen are not the same.
Euro style hinges adjust in all 3 directions that you'd want: up/down, in/out (relative to the cabinet wall), and front/back.
If you start with a cabinet carcase that's square or nearly square, it's usually a matter of tweaking some of those 3 adjustments on the hinges. (If the cabinet is desperately racked, you might exceed the adjustment range of the hinges. In this case, you need to correct the cabinet, then fiddle with the hinges.)
Note that the screws on those hinges are often pozidrive, so if you're doing a lot of this, you'd do well to get the right screwdriver. (Failing that, use philips, but be careful about stripping the screw heads.)