Where is your wedding location?
It is very important to keep your wedding location in mind when picking your theme. It can be much easier and organic to choose a venue first and then choose aspects of your theme after to ensure that the look of the event flows smoothly throughout.
Who are we as a couple?
It's a good idea to sit down together and jot down a few key words or phrases that define you as a couple. This helps as a springboard for possible themes that you connect to.
Do we want this to be a formal affair? Or more casual?
Knowing how formal or casual you want the event to be can help you decide how literal you want to get with your theme and help you come up with ways to incorporate it. Read: If you're having a black-tie wedding, you probably want to stay away from a hoedown theme.
What places have we been, or trips have we taken together, that have defined us as a couple?
Favorite travel spots or restaurants can help you choose a cuisine and define the environment at the wedding.
What is our personal style?
What does your house or apartment look like? Who are your favorite designers (interior and apparel)? Your wedding should reflect both of you and your personal style.
What mood do we want to create for our guests?
How do you want your guests to feel when they walk in? Do you want to focus on specific aspects of the wedding like the food or the music? Do you want them to be in major party mode, or lounging in vignettes sipping on a specialty cocktail?
What colors are we most drawn to?
When you look through wedding inspiration photos on Pinterest or Instagram (don't pretend you haven't), what images are you most drawn to? It's always helpful to save those images and look at them all together to find the common thread that pulls you to them.
Who are we inviting to the wedding?
Is this wedding mainly family, mainly friends, or a good mixture of both? If you have an older crowd or younger crowd, keep this in mind when selecting a theme.
What types of activities do we enjoy doing as a couple?
Do you like to surf, do you go to monster truck shows, do you love to go out to eat? All of this can help you define what the common bond is between you two and can be translated into your wedding day.
How are we going to feel about this looking back in 10 years? 20 years? 50 years?
You will be looking back on this day for the rest of your lives. Make sure that it is meaningful to you both and that you won't be kicking yourselves in several years for the choices you have made.