Where can I learn to use GPS to create property maps?

We have a handheld GPS unit and I'd like to learn to use it to create a map of our property. We have a large chunk of property (Ontario) that we're hoping to start farming, but it needs everything. Fences, clearing fields, creating roads, etc. I'd love to have an interactive topo map that we could use to plan. It would be great to be able to walk out to the field, say to yourself, "This looks like a good place to build a pond," hit a on and then you plunk it into the computer. Any good comprehensive DIY tutorial sites out there that I can learn from?