No work on these days, obviously. You should also blow some trumpets to celebrate. (Hint: God prefers a ram's horn.) Naturally, offerings are expected.
On Yom Kippur? Take the day off work. But make sure you're fasting all day. (Hey, this holy stuff isn't all fun and games.) Offerings? You betcha.
Last, but not least, is Sukkot. This celebration lasts for eight days and God has very specific details on which offerings you should be stopping by with on which day. (The ancient Israelites' livestock bills must have been through the roof.) On the plus side, there are more days off involved. (No word on whether or not God gives paid holidays.)