I'm just looking for any tips one might have for finding normal modes quickly? The GRE always seems to have a question or two on them and I have no idea how they expect someone to do a problem like that in the time given. I know that there is normally, in the problems given, a symmetric and an anti-symmetric mode. Is it honestly just knowing how the answers usually turn out maybe coupled with testing some extremes on the given answers? Thanks, I'm taking it on Saturday. After taking the final practice test available I realized I always skipped those problems because I just didn't feel I had the time to work them out.