I strongly believe the first thing you should do is pick the theme/style then pick a season. Picking a theme first allows you to set the rest of the wedding up based on that. You can pick your venue based on your style, your dress, your decorations, and so much more.
Then you should pick the season that caters to the style. Once you know what type of wedding you are having you can find a venue that works with that. Keep in mind these things. When picking a venue.
*Does it have room to fit your guests
* Does it have room to hold your events activities (i.e...are you having a cocktail hour?)
*Does it have space for dancing
*Is it too far from your ceremony?
*Can your it hold the entire wedding day there, or just the reception?
Also, if you pick your season then find your dream venue you can ask them what dates they have available. Instead venue hoping because you set a date first. Starting with these things will help you set the ground work for the rest of the wedding. Good luck!