Congratulations!  Since you’re marrying her, you love her.  If you love her, you want this day she’s dreamed about all her life to be magical.
Things to make sure to get in order:
  • Where you are getting married (this is fun - try the food)
  • Your ceremony & vows
  • Officiant
  • Photographer and Videographer (get a good one)
  • Cake (these aren’t normally tasty - save a piece for a year)
Stuff you should do:
  • Handle your side of the guest list
  • See a couple venues and try a couple cakes
  • Make sure your groomsmen are timely and presentable (wife picks attire, within reasonable budgets)
  • Help out w/ party favors, or something fun
  • Spring for an Open Bar (this could also just be unlimited beer & wine)
  • Spend on at least one “fun thing” that you both want
Cool ideas if low on cash:
  • Venue: Park, Restaurant, or City Hall
  • Cake: Bake it
  • Photographer: Get friends to take pictures and video (make sure to record it)
  • Food & Drink: Have people bake pasta / ziti and bring champagne / wine / booze
  • Men’s Attire: White shirt and khaki or jeans; just all match
  • Dress: Sample sales, etc.  < $100 is possible; get something white though
Day of Wedding:
  • Make sure to plan to not be hungover and get 5-6+ hours of sleep
  • That morning, make sure to eat & drink water
  • Don’t be drunk (until after ceremony, then it’s ok)
  • Relax.  Everyone who is there loves you or they wouldn’t show.  Enjoy it and soak it in.
Hurricane Irene hit our wedding and it was the best day of my life.  So above all else, don’t sweat the small stuff!  No one cares if the cake is stale or people walk out in the wrong order.  
That said, don’t puke at your own wedding while the music is still playing.