Photographers: I need some tips for sky stars photography (night photography)?

I will take some photos tonight for "perseids".
I have a Nikon d90. I will use ISO 800 f/3.5, 30" and a tripod. I'll leave the city.
But, could you give some tips to get great photos? I'd really appreciate them.
Thanks
(sorry for my english, It's not my native language)

This link will probably answer all your questions.

http://www.danheller.com/star-trails