Another skill that separates the pros from the amateurs is comma usage. Personally, I don’t know all the specific grammar rules that apply. There are also a multitude of usage opinions. I actually had an English professor in a university level grammar class tell us they were optional! If he were still alive, I would write him a strongly worded letter regarding why he was all wet.
Granted, there are some who could be called “comma fanatics.” For example, there’s a lot of controversy over what is known as the “Oxford comma.” Most people seem to understand that the elements in a series need to be separated by one. However, whether or not to place one directly before the “and” that precedes the final item is less clear. Most readers can deal with that situation one way or another.
However, with complex sentences, commas help keep the statements from running together. Think of your dinner plate, how most people prefer to keep the meat, potatoes, vegetables, and anything else separated, as opposed to being all slopped together. Commas do this for long sentences, keeping the thoughts separated and more coherent.
Another classic example of how commas change meaning is “Let’s eat Grandma” versus “Let’s eat, Grandma.”
Without knowing all the rules, one way to tell intuitively where a comma belongs is to read your final edit aloud. Where a pause is necessary for clarity is usually a good place for one.