I have been playing a shaman since a little after Burning Crusade came out and have worked through many a patches and Wrath to get where I am now doing OS, Naxx and even a little Ulduar. I will attempt to help newer shamans to get ready for raiding Naxx and Ulduar.
1) Glyphs - The glyphs you choose are very important for a shaman, they can help you in such great ways. For an Elemental shaman, I would suggest taking Glyph of Flame Shock, Glyph of Chain Lightning and Glyph of Water Mastery as your 3 major choices, you can pick anything you want really for minor glyphs but I strongly suggest taking Glyph of Water Shield and Glyph of Thunderstorm.
2) Builds - Builds for Elemental Shamans are pretty generic, here is the best one going right now. Elemental Shaman Build
3) Gearing - Whenever out raiding or doing heroics, always be on the lookout for +SP, Crit or Hit rating gear, whether it be Cloth, Leather or Mail, if it's an improvement try and get it no matter what it is. Its a good idea to get the Barricade of Light you can get from badges, it is a good Resto/Elemental Shaman to start off with, and even better if you are dual speccing.
I may do a small thing on Resto Shamans also, but I am no expert lol.
Good luck guys and have fun with the raiding and gearing!
My Shaman, just for refrence.