When I'm building macros, I try to break them up into sequences that fit together. For my paladins I have my base sequences which center around getting and using Holy Power. Any secondary sequences will be things like fillers. For my Enh shaman, I have it broken up with strikes in one sequences, shocks in the other.

As for seeing what's getting cast and what's getting missed, the simplest way to do it is go to a training dummy, pull your spells out of your spellbook and onto a blank bar and start casting your macros. Tedious, yes, but it's a lot easier to spam away and visually see what's getting hung up or what's sitting off cooldown too much.