After underwriting, the lender adds "conditions" that must be satisfied by your broker, yourself, or whomever is getting you the loan. Once underwriting is done, that just means you have a "conditional approval." If you don't satisfy all the conditions, your loan can not be approved.
Once you get full approval and the "clear to close" that's when you know you're ready. You should get a call from either the closing agent or broker to schedule a time to sign the documents and transfer the deed and get your keys.
At the closing, you get to sign lots of papers, and review lots of legal jargon. It's nothing super special, mine only took 25 minutes.
Mortgage underwriter, homeowner