It's actually better to use "said" than other words because it's nearly invisible. Using other words is seen as the mark of a beginner.
Essentially the two things you want to avoid (which might be the opposite of what you were taught in school, actually), are lots of adverbs and verbs other than "said." This is typically viewed as telling the reader instead of showing them what is going on. There are some basic exceptions (and even adverbs can be used if they're used sparingly) for an occasional, "whispered" or "shouted," or something like that, but those shouldn't be used all the time. The idea is that you want the words
within the dialogue to be the ones conveying how something is said.
For instance, say you write a line like this:
"How could you do that! What were you thinking?" he shouted angrily.
The dialogue itself shows that she's angry, and even gives an indication that it's being shouted. If it's already obvious because of the dialogue, then it comes off as almost condescending because you're implying the reader wasn't smart enough to catch it. If it wasn't obvious in the dialogue (for instance, "Why'd you do that?" he shouted angrily.), then it's being used as an excuse to tell the reader how the words were said instead of showing them by the words themselves. Considering the writer's number one goal is to show the readers what is happening and allow them to see it in their minds, this is also not a good thing.
So as a general rule, it's best to stick only to said. You can also use occasional actions instead (I do this a lot), bonus points if the action is actually relevant to the story. For instance:
Beth waved the perfumed letter in Bob's face. "What the hell were you thinking? You thought I wouldn't find out?"
Or something like that. Bad examples because they're just off the top of my head. But yeah, this is the basic gist.
The hardest part of dialogue is the dialogue itself and making it sound like real people talk. If you can succeed in that, the rest will come naturally. A good way to do this is to go somewhere public and take a notebook and just listen to what people are saying, maybe write down certain phrases, and then try to imitate that in your writing. Good luck!
http://www.musik-therapie.at/PederHill/Dialogue&Detail.htm
There's a great site about writing dialogue that's much better than my explanation.
