I didn't go for a hair trial before my wedding. What in the world was I thinking?! Even though I absolutely loved the way my hair came out for my wedding, I don't know why I had so much faith that I didn't go for a trial!
I strongly recommend you do a hair and makeup trial before your wedding, perhaps 3-4 weeks before your wedding is the perfect time because you won't be too busy with the last minute details and your hair will be about the same length on the day of your wedding.
When you go for the trial, make sure you bring a picture of what you have in mind so that your hairstylist know exactly what you want. Also remember to bring all your hair accessories with you, veil, hair jewelry, tiara, etc. so that your hairstylist will not be caught by surprised on the day of your wedding.
Bring a family member or a friend with you to the trial to get her honest opinion. Have her take lots of pictures of your hairdo for reference.
Here's a wonderful website you can go to to upload your photo and choose some bridal hair styles you might want to try, at least you can see it on you before you do the trial! Isn't that wonderful? The Hair Styler has lots of ideas for all types of hair, check it out.