The internet doesn't need any more wedding planning checklists, I know. You've probably read a few. But I do want to add to the chorus of "DO THIS FIRST!" from wedding planners everywhere:
Decide how much you want to spend.
This means different things to different couples. Some know for sure that they cannot go over a certain dollar amount, no matter what. Others have a dollar amount that feels comfortable, but wouldn't lose any sleep if they went a little over the top. A few start out saying they'll spend whatever it takes to get what they want. I've known all of these couples, and the ones who have the hardest struggle are the ones with the "whatever!" budget. I know, I was surprised when I started noticing this, too!
You need to identify what some of us refer to as your "freakout number." If you spent x dollars on your wedding, would you freak out? Once you find that, you can scale back to something that doesn't scare you (don't forget to include a cushion, because so many clients go over what they thought they'd spend). It shouldn't scare you! Once you are comfortable with your target spend, you can start doing research to split it into categories and make decisions with much more confidence.
An important detail to add here is that your overall spend doesn't mean much until you've figured out an approximate guest count. But if you start with a number and an even a tiny bit of a vision, you can figure out what's attainable. $40,000 goes a long way with a guest count of 40, but not nearly as far with a guest count of 400 -- especially in a big city -- even if you're just thinking about food and beverage. If you can trim your guest list, your budget per guest will go up, and that could open up options like nicer tequila, more flowers, or a couple of extra pieces in your band.
That's your wedding planning homework...and one of the few things you really wouldn't want your planner to do without you (seating assignments are another). Pick your number first!