Have you been rated for comps?

Hi,

I plan to be rated in my next trip. Since I have never
done it before, I have a few questions.

* How long does it take them to rate a player?
Ten minutes? An hour?
* If I'm aware that they are watching, is it a good idea
to make some bad plays?
* How do I claim the comps? Only at end of the trip,
with the receipts for room and food?

Could anyone share the experience with me? Thanks.

TJ