The first thing after getting engaged is to set a budget and determine who will be paying for what. The national average wedding cost is $28,427 (2011: The average was $27,021) according to The Knot. They key is not to go into debt for your wedding. Open up a separate account and put away money every week/month to pay for wedding expenses. The biggest piece of advice is to pay by check/Debit card and not by credit card. By using a credit card in the end you will be pay more for that service with the accrued interest.
Here is a helpful chart on where to allocate your money for your big day.