Deciding what's most important to you is the first step in bringing your vision to life. Your budget begins to materialize, and the planning process cranks into gear. If you've always wanted flowers then you certainly deserve a wedding filled with lush blooms. Now, if you're a stationery freak (as I am!), then invites will be your "thing" (it's perfectly alright to have more than one by the way).
Bottom line, YOU know what you love. I suggest starting with assigning priority similar to the example above. Once done, you can easily determine which elements should get more of your money and your time.