Bring protection. Make sure that you bring ear plugs with you to the concert and that you use them properly. The best ear plugs are those that can be molded to fit your unique ear shape exactly.
Distance yourself. If at all possible, try to put some distance between yourself and the giant banks of speakers that exist at most concerts. The closer you are to the speakers, the louder the noise you're exposed to, the better your chances are of significant hearing loss.
Take a break. If the noise from the concert seems especially loud, take a walk away from the stage and visit the restroom or go get a beverage. Taking a short break from the concert's loud noise will give your ears a chance to recuperate and will help to mitigate the damage that's done to your hearing.
Don't speak. Although it's tempting to converse with other concert goers doing so is extremely difficult and can cause hearing loss. Removing your ear plugs will subject you to the loudest noise possible and you'll have to scream louder than the music to be heard by anyone. This extremely loud noise can cause serious hearing loss, especially when it takes place right next to your vulnerable ear drum.