Comma,

Careful with the comma.

Limit them. At least favour the full stop.

A sentence cluttered with commas may be hard to follow. Your reader might drop out, or they might be forced to re-read it.

Think about them as points where your reader might take a breath. Read your writing aloud, and place commas where they make sense to your ear. Just make sensible judgements. There are no hard rules, no matter what any strict grammarian might dictate.

Lots of commas are the smoke to the long winded sentence fire.

It's OK to have occasional long sentences. They play well with both short and medium ones. But if you're unsure whether to use a comma or break a long sentence in half with a full stop, choose the full stop.