Start off by going to ebay to determine the current resale value of your timeshare. Most timeshares are selling for 0-10% of original retail.
Go to ebay
Search for your resort by EXACT name
In the menu on the left, click on COMPLETED AUCTIONS
That will show you what it's actually SELLING for
If the resale value is low, then it won't be cost effective to use a broker, because they charge a commission of $1,000 and up. There are definitely reputable brokers, but for a low or zero value TS, it doesn't make sense to pay commission.
If it has no resale value, and you want to give it away - we have a forum for that on TUG: http://tugbbs.com/forums/showthread.php?t=132509
WHATEVER YOU DO, DON'T PAY ANYONE A HIGH UPFRONT FEE - THOSE FOLKS HAVE NO INTENTION OF SELLING YOUR TIMESHARE - THEY JUST WANT YOUR $$$.