One good place to start that I know of is to go look up your class and spec in the ElitiestJerks forums and look at the information they have on the class and spec that you want to play.
The first things I'd do before getting to in-depth is look at what glyphs, talent builds, gems, and rotation in the post that they will have on your class. Later you will want to get into reforging your gear to maximize your dps or really anything, but I'll be covering that part in the next post I make on this topic.
Right now the character I've been playing the most to gear up has been my Shaman who is pretty decently set up to raid with. I'm doing about 13k usually in heroics on my shaman which from what I understand is actually higher then you need to be doing before you are looking to start at a entry level raiding guild, but I'm quite satisfied with my ability to dps. Lets use him as the example though.
I hadn't played Enhance in some time and I wanted to try it out again and see if I like it now, I never use to, so I got some agility mail gear then went to ElitiestJerks to get information on how to do the best I could when I went in a heroic and tried it out. I don't necessarily read everything they have on classes as a fair bit of it goes over my head, but on of the first things I look for is a talent build to use.
Now with the Enhance Shaman as I'm righting this they don't actually lay out a build to use, but do point out recommended talents and the build I'm using is a pretty common one I believe and you can find it here.
The other thing I look at is the glyphs, for enhance the only must have prime glyphs are Glyph of Lava Lash. other choices are Glyph of Stormstrike, Glyph of Feral Spirits, and Glyph of Windfury Weapon. I'm using Stormstrike and Windfury weapon aside from Lava Lash at the moment on mine, though I do need to set down and Sim all the other choices to find out whats best for me.
Gemming, keep in mind after you sim you character you may end up changing your gems, but you can just sorta go with what they recommend for the most part and usualy with most dps classes, less the socket bonus is 10 of your primary stat, Agil for Agil users, Int for caster, and Str for Warriors and DKs, 30 of a secondary stat, crit, haste, mastery, you want to strait up stack gems for your primary stat.
Now that we have that information we need a rotation, though keep in mind that there really aren't any set in stone rotations anymore. You don't just go in and do this, then that, then the other thing and repeat those steps over and over again, though for a certain portion of your dps, you are sorta doing just that.
Enhance shamans the priorty of abilities is searing totem when its not up, lava lash, flame shocks with Unleash Elements, Lighting bolt with 5 stacks of maelstrom, Unleash Elements, Stormstrike, Earth Shock, spirit wolves. on single targets
You'll want to practice using those abilities from first to last in priority over and over again either doing heroics or on training dummies over and over again. Sometimes you might want to watch a video on the rotation to help you get it down more.
Couldn't find a good video on the rotation, I have seen one before, but just for now will put this one, its pretty wicked fail though so..yeah..
