Optimising sitemap

This is for the techies out there. Am just wondering about sitemaps. I have forums and have managed to get rid of the sid, but now when i auto-generate a sitemap then i am getting hundreds of pages off my site and half of them are irrrelevant.

Does anyone know which bits of the forums i should exclude? I mean I don’t want to exclude /forums/ alltogether, that would just be silly… but the /templates/ maybe? And if I were to exclude the templates then would it cause google problems?

Helppp

Thanks

Bart