Wedding Planning 102
You may already have a stuffed wedding binder or a Pinterest page with boards for every great idea you have collected since before you were engaged. Now what?
It does seem overwhelming, doesn't it? Because you are an adult, you know things don't usually turn out perfectly. But you can still have a wonderful wedding. Remember your "why"* and take a deep breath.

The starting point is your budget. Being honest with yourself here will help you make all the other decisions and save you from a mountain of bills after the wedding. Now think about what is really important to you and your partner. Do you need a carpet of flowers to make the day memorable, or is the food a higher priority? Maybe it's having a rocking dance band. Or setting aside funds for a terrific honeymoon.
Next take that budget tool from the Knot or Wedding Wire (search "wedding budget calulator") and play with the numbers. You will come up with some approximate amounts that will guide you in your search for affordable vendors. It's better to know your budget before you get your heart set on working with an award winning florist or popular caterer. With a little bit (ok, a lot) of research - or a wedding planner who knows - you can find budget friendly options.
Then use a planning tool to schedule all those details. Be honest with yourself about how much you can do. Enlist willing family and friends to help. Consider hiring an experienced wedding consultant or designer to help you sort through the piles and simplify if you need unbiased advice (sometimes, friends can be a little too helpful), before the stress level becomes unmanagable.
Remind yourself of the outcome you want. Keep focused on your "why". It's gonna be a great day to celebrate!