One of the main problems I see in books I critique is not being able to format dialogue correctly. So instead of tagging everyone in critiques where I've shown others how it's done, I've decided to make a page with the tips.

Okay, take a look at these examples.

"Morning," said Linda. Her lips split into a huge yawn. "Man, that mattress was comfy."

Notice how there's a comma before the dialogue tag? And that after the full stop there's a capital?

Here's another. Starting with action this time though.

Tom stirred his coffee lazily. "Well I go shopping for beds every year." He placed the spoon on the marble worktop. "Costs me a grand each time, they do."

Notice here how whenever there's an action, there's always a capital?

GROUND RULES:
Dialogue tag = comma + lower case
Action = full stop + capital

Hope this helps^