Here are a few examples:
1.) Notice I'm using a small first letter here for the dialogue tag. You can never use a period to end your character's dialogue with this type of tag.
"Hi," she said shyly.
"What are you saying?" he asked.
"Oh no," the girl exclaimed.
2.) Period, capitalized-first-letter format. Conversely, you can never use a comma to end your character's dialogue for this type of tag.
"What?" He looked at me angrily.
"Thank you." Her voice was cold when she said the words.
"Hmph." That was all he said - hmph.
ADVERBS IN DIALOGUE TAGS
Now, if you've started reading books on how to write fiction / novels, then you'd probably have noticed that editors are very much discouraging when it comes to the use of adverbs.
"I hate you," she said furiously.
In this case, there's no need for the adverb since you can infer the character's not feeling predisposed to whoever it is she's speaking to with her dialogue alone.
"I hate you," he said quietly.
Ah, but in this case I think an adverb is warranted. Because you gotta wonder - why did he say such powerful words quietly?
WHEN AND WHEN NOT TO USE DIALOGUE TAGS
It's a subjective matter, but it's safe to say that you don't need to use it all the time.
P.S. Please do not consider this post as an indication that I'm a great writer. I am not.