The AP Style Guide (my go-to resource for writing rules) has six sections devoted entirely to list formatting. That’s insane. I’m going to try to simplify it down to just a few key ideas.
General Rules for Lists:
Capitalize each first letter.
Put a period after every complete sentence (like in this very list).
Put a period after every item that completes the introductory stem.
Leave the period off if it’s not a complete sentence on its own or does not complete the introductory stem.
Stay away from semicolons.
Keep each point less than three lines. If it’s longer, you may as well just make it a paragraph.
Number your list when you have more than five points (like this one). It makes it easier for your readers to track and refer to them.
Avoid lists when you want to build a relationship or deal with a sensitive issue. Bullets and numbers convey orderliness rather than cordiality.
Here’s another example:
I went to the store and got
A new stapler and staples.
Some tape and a dispenser.
Fruit Loops and chocolate milk.
See: The list items are sentence fragments, but they complete the introductory stem (I went to the store and got) so each one gets its own period.
Here’s an example of a list that would not need periods:
The agenda is as follows:
These items don’t need periods because they do not complete the introductory stem and also are not complete sentences.
Hope this helps clear things up for you! Until next time, happy writing.