The Knot.com is a resource for everything WEDDINGS.  They've put together a list of things you should plan first after getting engaged.  

FULL LIST HERE

1. Set a timetable - what time of year do you want to walk down the aisle?! 

2. Dream up style/Pick Location - after you've set a date you can check availability on your favorite venues.

3. Set your budget - This is essential to set early in the process so you have a gauge on your finances.  Nothing can ruin a wedding quicker than going thousands and thousands of dollars over budget.

4. Draft a guest list - this will go through several phases, it's good to start on this as soon as you can.

5. Register - what many consider "the fun part."  Time to get registered at your favorite stores before showers begin so your guests can buy you gifts!