A vast majority of timeshares are only worth $1 so the first step would be to determine what you own. If you own in Orlando or Vegas, then most likely you have a timeshare that has no value. You don't need a company to "sell" this type of timeshare. Give it away yourself on TUG for free. If you own DVC or a prime Marriott or Hilton, then there may be some value but even Marriott and Hilton have some timeshares that are worthless on the resale market.
If you have a low value timeshare don't get suckered into paying a company to advertise or market your timeshare. In most cases, they will deceive you about the true value of your timeshare. It won't sell but you would be out a significant upfront fee.
If a mod sees this it appears that the OP's question was posted to the wrong forum.