Determining the value of any collectible, including Hot Wheels values, will always be a less than perfect science. So many factors influence the value of a collectible, and the subjective nature of "value" means two people may have completed different outlooks on the accepted value of a hot wheels car.
But in general there is usually an agreed upon minimal value for any item, although again this does fluctuate over time - if you're looking to determine your hot wheels value, the best place to start is somewhere that sells a lot of Hot Wheels - certainly the Toy Peddler fits that bill. Look at current prices for listed items, at recently sold items and find out the going rate for different cars.
Keep in mind that many factors affect value, including condition, variations, colors, and personal preference. In order to sell on the site, you'll simply need to create an account and purchase listing credits in order to post your items. You can host your own photos or use our internal photo hosting, and posting an item is a easy through our one page form. Your Hot Wheels item will go to the top of the list in your chosen category and on the Listed Today page.