1. Pay attention to the hand she gave me to put the ring on. Oh well, not sure anyone noticed.
2. Tapped the keg much earlier in the day for the reception. I had no idea that it needed time to settle.
3. Make sure we had someone to get the snacks out while we were taking pictures. Seriously, have one designated person, who is not in the wedding party, handle stuff like that.
4. Find a different caterer. While the food was pretty good, they missed the vegan plate for my brother-in-law, despite us being really,, really certain it was covered. Drinks and water were a disaster. I really think we could have just brought in a fuck-ton of tacos, sodas and water and we'd have been good enough.
5. Make damned sure the jeweler's idea of the ring is clearly the same as yours. We had a custom ring made for my wife and I think the jeweler failed to take good notes and the result was bad, very, very bad. We had the ring re-made, after it was presented and before the wedding. Her ring was very nice for the wedding.

But, not a lot. Sure, the year or so before the wedding was stressful. We did the planning ourselves, put together complex invitations, "save the date" fridge magnets and all the programs. But, because we did give ourselves a year to get it sorted, we had the time to find what we wanted. We had also been living together for a couple years by the time we got married. So, it was more a "ya, we should probably finally do this" than any sort of pressure to "start our life together".