I love using lots of dialogue in my books. Overall, I think this is a good thing, but it means that I'm constantly reminded of how clueless I am when it comes to the rules of punctuation and form. It doesn't help that it's next to impossible to get a straight answer that I can understand about what should be capitalized and what shouldn't. Most of the explanations come with words about clauses and direct and indirect subjects or something. You do know that they don't teach grammar in grammar school anymore, right? I am a product of the "whole language" approach to language arts. I think they should change it to "no language."
When I Googled, I found this short article on How to Punctuate Dialogue Correctly. Pearl Luke claims there isn't much to remember when it comes to punctuating dialogue. Whatever! There's a lot to it. It's bad enough I have to sit there jotting down what the voices in my head are telling me (oh yes, I have that going on). I don't want to worry about some anal picky person looking at the page and shrieking, "Oh my God! Don't capitalize that word! Noooooo!"
I'm starting to think Cormac McCarthy had the right idea with The Road; forget about punctuating the dialogue at all and say, "I'm writing Literature. I don't need to worry about that stuff."