I worked on this last summer. Actually, we did Parts 1 and 2 in rep. There's no real trick to it, it's a fairly straight-forward Shakespeare show. As always, keep your envelopes and letters straight! The hand props in the Tavern can get pretty crazy too. Ask for tankards that can take a beating from being thrown around, and plenty of dishtowels if you're using real liquids.
The first thing to do is to get the particular script the director wants, and make sure that the cuts are precise. It's best to get the cut script to the actors, rather than the full script. Especially in this show, where Falstaff's gang of thieves will probably be cut down to fewer bodies and their lines re-assigned. Our adaptation ran two hours twenty-five minutes with one intermission (which I believe was right after Hal's return to court "I know not whether God will have it so...") and a full version would come in over three hours, I bet.
The fights in Act V can get pretty hairy, it's true, but you'll probably end up with only three or four two-handers plus the single Henry/Hal/Douglas three-hander. Keep an eye on the choreography and suggest that Falstaff's choreography be kept to the absolute minimum (he'll be struggling with lines!) If you're using broadswords, make sure your fight captain knows how to maintain them, and keep giving the note to slow down the fights once you're in performance.
About Falstaff - if your actor is padded (i.e., not a plus-size himself), work with the costumer to keep his costume breathable and lightweight, so he doesn't die of heat exhaustion onstage!
That's all that occurs to me right now, if I think of anything else I'll try and enter it.
Have fun!