I would suggest a type of canvas called Sunforger. It is lighter weight than canvas duck. Sunforger is also waterproof and flame resistant. Mostly it only comes in natural color, that would be a beige/tan canvas color.
For sewing, don't ruin your nice modern sewing machine on canvas. A older sewing maching with metal innards works best, you do not need a industrial sewing machine if you are only making one tent. Flat felling the seams is a good idea, but at a minimum you will want to fold the selvage edge to one side and sew it down.
Use size 18 (jean) machine needles, they will not break as much as the lighter weight domestic sewing needles.
Thread, you want your thread to be about the same weight/strength as the threads in the canvas. I use a heavy nylon thread.
For overkill, you can use a seam sealer for tents. It's a good idea if you live in an area where it rains a lot. If you do not use Sumforger canvas, there is a product called Canvak available from Cabela's, that will work for your untreated canvas.
Cynthia, yes, I've made a few &%$@*!! tents.
