Your h-entries should have, at minimum, the following properties:
e-content — the main content of the post
p-name — if your post is an article with a name, use this classname.
dt-published — the datetime the post was published at, in ISO8601 format, with a timezone
u-url — the canonical URL of the post, especially important on pages listing multiple posts
It’s a common convention for the published datetime to be a link to the post itself, but they can be separate if you want.
There should also be some way to discover the author of the post — either link to your homepage (which should have your h-card on it) from anywhere within the body of the page with rel=author, or optionally embed a p-author h-card in the h-entry.
The web is an expressive medium, and as such there are many other properties which you can add to your posts. Check out the h-entry documentation for a full list.
Want to be able to use h-entry data in your code? Check out the open-source implementations.