I think first (ok, maybe not the first, possibly the third or fourth) thing that comes to mind about planning your wedding, is what to wear. For the groom, this seems like an easy answer. So we'll start with him first.
Time of Day (and how long of a day....)
Ok so I know what you're thinking; the ceremony isn't until 5:30. It's an indoor ceremony and I can take my jacket off during the reception. So even though I picked a heavier suit, I'll be fine. Having been to hundreds of weddings, I can't tell you how many times I've heard the guys complaining about how hot (overheated, not sexy) they are in their tux. Sweat stains on your collar is not attractive and no, I cannot photoshop this out of all 3000 photos. Make sure you talk with your bride/wedding planner/mother-in-law about the timeline of events for the day because this will determine which style of tux you choose for yourself and your dudes. An example of this would be if you decide to do your formal portraits outside at high noon before the ceremony.
Remember gents, you have to wear your wedding-day get up all day. On average the groom will wear his tux for 10 hours. Imagine having to wear it to work. If you're not comfortable in the dressing room, you won't be comfortable on the dance floor, no matter how dashing you look.
Location, Location, Location
It may be obvious, but the location of your wedding day is probably not the first thing you think about when planning attire. You want to look great all day. Example: You have your ceremony early on the beach in your linen tux and then everyone piles into limos to go to the cocktail hour. Linen tuxes wrinkle terribly. So by the time you arrive and climb out of the limo, you are all a wrinkled mess.
One trend right now is going jacketless for weddings, especially in the summer. Because it's a much less formal look, you and all your men should be matching. All tucked in? Make sure everyone has belts and that they match. Grab an extra, because there is always one person who forgets or will grab the wrong color belt. Again, photoshop can only do so much. No tie? Undo the top button of your dress shirt.
Shoes and Socks
DON'T FORGET THEM. And, bring an extra pair of both for later. Tux shoe rentals are probably the most uncomfortable thing you will ever put on your feet. They're horrible. By the reception you will want to change your shoes. Your feet will thank me later.
Ok, so you've been running around all day in your tux, now you're tearing it up on the dance floor, when it hits you. The stinging, burning, itching, inferno starts to brew in your briefs, until you want to pour your champagne between your (other) cheeks. Make sure you or your partner packs some talcom powder. Or better yet, I recommend Anti MonkeyButt. Awesome stuff.