Tip #2 which I will cover in my class this September is never wait till the last moment to figure out what you are packing for the trip, or for wearing to the wedding, don't procrastinate.
We of course know this intuitively but many do not act on it and that is when we make our most mistakes. We buy what we don't need or want because we feel like we are trapped.
If you buy anything that is dressy or semi formal or formal it is going to need alterations and for that reason alone never wait till the last minute to shop for that "outfit".
If you have an organized approach to an event most often you can wear something you own by updating it with kick-ass new accessories. In the event you really need a new dress or suit or formal wear give yourself at least 6 weeks to shop, alter, prep around the outfit. If you stay focused, calm and organized dressing for events or packing for trips does not need to be such a chore.
Keep a calendar of important dates and back out a six week date to start gathering your thoughts on what to wear and how to shop for the event.
My best advise if you really are stuck pay for a personal shopper/stylist to help you with the process, it is worth the money!