Great advice here. The only thing I would add is that if you are being pressured and the above responses don't work, excuse yourself and walk away. It can be as simple as saying you have to use the restroom.
Also, as has been stated in other posts about this, we tend to make a bigger deal about these situations than they turn out to be. While it's good to have your responses ready, also be prepared to have people accept those responses and not make a big deal about it.
(Edit - I didn't see Anvil's reply and basically said the same thing)