A season/month is a good place to start. After you have settled on a location you can start checking on specific date availability. Most resorts have up to 2 weddings/day.
As far as October, it depends on where you want to go.... Hawaii, Mexico, Bahamas, etc...because of different rainy/hurricane/etc seasons.
After that, I'd choose a travel agent...they have traveled to a lot of places & have stayed at all kinds of resorts, so they will be a great resource. Plus, they can help you get the best rates for you & FI, and guests.
I remember being in the same place you are back in March. This site is very helpful, tons of resources, and brides (ones who have recently married and ones currently planning) are willing to offer suggestions/advice/feedback on their experiences. So, Try cruising this site more.
Also, check out the "resort reviews" section.
I hope this helps! Happy planning!