My rules of thumb when setting up for a match are:
-Always have at least 1 more defender than the oppo has strikers (if he only has 1ST you can get away with 3W or 3N and put red arrows on either the wingbacks or the DMC if you're using one)
-Always play a DMC if the oppo has an AMC
-Don't play an AMC (or possibly play 2 of them) if the oppo has a DMC
-Use long passing against a flat formation, mixed otherwise. If you're getting 80% possession due to an opponent's illegal/out of position formation it's worth playing long ball - I have a theory that often the "bonus" possession gets wasted playing tika-taka in midfield otherwise, and if you can give your strikers the ball a lot they'll get through eventually
-A DMC is really useful against 3MCs, as otherwise every now and then one breaks forward and gets a shot off from the AMC zone
-Only use down-both-flanks passing if you are fielding more wingers than the oppo. Use through-the-middle with narrow diamond (and I guess 4-3-3 - I only have 3 strikers in my squad so have never tried it).