I recently went to Canada, one of the photos I took was fantastic and I contacted a company to see if they would like to use it. They said they loved it and asked me how much I would like for shared rights to the photo. I have never done this before and have no idea how much to ask for. can anyone advise. They want to use the photo on their website and for marketing purposes.

prairie son

First I would find out what the web site is and what kind of marketing they plan on using it for. The longer the time involved plus if the web site and marketing plans are going to be seen by many people, the price should higher. DO NOT agree to unlimited rights.
Also, set a time limit on how long they can use it.
Since this is your first time to sell an image you won't be able to command the same price as a seasoned stock shooter. Also, the contents of the image helps determine the price.
Take a shot and start at around $5000 for one year shared rights.
Prairie Son, retired Pro Photographer

Fr_Chuck