The most important thing by far to remember when being a bridesmaid is to support the bride. This is their special day, and your job is to make sure everything you have control over goes to plan and the bride stays happy.
Things may go wrong; the commissioner may not show up, the food may be an hour late, what ever it is, you need to be a calming presence for the bride. Your wedding planner will handle these big situations to the best of their ability, but your job is to keep the bride from freaking out. Do what you can to help in any situation and take care of any of those little last-minute things, so the bride and groom don’t have to worry about it.

This also includes not causing any drama or helping to prevent drama. We all know there is potential for things to get out of hand especially when alcohol is involved. Don’t be the one to get drunk and cause a scene with one of the other guests at the wedding. If you see a problem unfolding, try your best to deescalate the situation before the happy couple must get involved.
Make sure you know the full plan for the weekend. Ensure you are available for the rehearsal, any hair or makeup appointments, getting ready, pictures, and any other wedding events that may be planned for the weekend. You are there to stand by the bride on their big day and you need to make sure you know what is happening and to be there if she needs anything. Do not be late to anything!
Overall, you are there to make things easier for the bride. Give opinions when asked, go grab that extra pair of shoes from her bag when the heels get to be too much, and do anything you can to make their day the best day.
-Taylor MacDonald, Imagine Events