I am thinking about putting some of my designs on here for bidding / sale, but I see a lot of people offering "full rights" and a few offering "exclusive rights". How does one go about getting rights for something they have made from scratch / with stock images. More importantly, how does one go about selling or giving the rights to a design?
Well if you have made something from scratch you automatically own the right - the "copyright" - to that work. You don't need to apply for a copyright, it is automatically denoted to you when you create an original work. You are then able to sell, exclusively or otherwise, the rights to whoever you like.
If you are wanting the sale to be watertight then you will need to sign a contract.
Remembering that if you are using "stock images", someone still owns the copyright to that original work. It is best to check that you have the permission of the copyright owner to alter the image - because if it is a recognisable derivative and you do not have their permission you are in breach of their copyright.
To be honest it's best to see if you can have a look for similar contracts as the wording needs to be quite precise ... the laws pertaining to the Internet are still heavily under development and many areas remain untested - but it's just a standard IP issue really.
Google may just be your best friend - if I find any sources I'll let you know.
And this site seems to have some good examples. You'll need to read through the full contract to make sure that it is relevant to your situation. The "Total Assignment of Copyright" and "Nonexclusive Copyright License" are probably the ones you're looking for.