So now that you have an approach in mind ... what are you really facing? Please prepare yourself to deal with some heart issues at the sales table. The product and their offer ($) will likely be attractive, desirable and deeply tempting. Indeed, timeshare can be a very good thing: lots of space in large units; kitchen; laundry; "become part of our family"; VIP-perks; etc. They are selling an attractive product; it is very natural to want the product, the lifestyle, the locked-in future vacations, etc.
Guilt. If they can't win you over via desire -- they may try the guilt avenue as mentioned above. The angle may be one of "wasting their time" or "letting down your spouse" or "letting down your family." Prepare yourself to say, "Hogwash!" to each of those ploys. If attending as a couple, do not allow them to play one off the other.
Secret knowledge. One tactic may be to discredit everything you've heard or read from your trusted internet forums. Once they've got you second guessing your "expert base" they will start dangling secrets you can only learn from them. Most of these are about unwritten changes coming down the pipeline that will seriously damage all the old methods causing everyone to buy "new" from the developer again to be reinstated. Again, "Hogwash!"
Take away. If you don't buy today, directly from the developer, you won't ever get <name a feature>, <name a location>, <name a holiday reservation period>, etc. The 'take away' tool creates motivation to "protect what is yours" even before you own it. Once you start to protect it, your mind has already jumped over the hurdles of buying it ... it is "yours" in your mind. Signing the paperwork is simply a formality. If the conversation goes down this path, think of giant red flag and remember this thread!
Confusion. Developer math is a special study. Yep, developer math can justify huge purchases! If you can't follow the numbers as quickly as they are working them, ask to take the sheet home for a day or two to review. Don't sign a contract agreeing to buy before your study. Insist on reviewing those numbers thoroughly before signing anything.
Be prepared for psychological sales tactics. These folks are experts. If pressure works, they'll use pressure. If sweet talk works, they lay on the flattery. They'll figure out your weak spot and use it against you. You've been warned. Good luck!