I've always wondered about this. Is it really not possible to come in with the attitude that I would never buy a timeshare and that I'm just going for the cheap hotel stay? Are they that talented?
I have done it multiple times and have stayed strong.
I think if you have the right mindset going in you should be fine. The ever changing offers can be really quite good and worth it IMHO.
A couple of pointers:
1. Make sure to tell your DW not to even consider it no matter what (she was starting to consider it
). I think the sales team know they may be swayed more easily so they require both to attend!
2. There are different ways of responding to the sales team that I think may be effective (at least for me):
A) Just to beat the horse and keep saying not for me, not ready to commit, cannot afford it etc.. eventually they will relent.
B) Tell them you pay for vacations with points and miles accumulated from
everyday and bonus spending 
so why would you pay hefty monthly timeshare payments!
