If your gonna trying hunting them in the daytime without a hound Woodduck is on the right track. You have to kind of develope an eye for spotting coons. They'll often have "lay up" trees, not den trees, where they will lay in a crook of the tree or something for a daytime snooze. You gotta look for lumps, tails, ears, some times they blend in pretty darn good.
If you've spent any kind of time in the bush, you've probably walked past a lot of coons; of course your not typically looking up in trees (unlike the deer we're hunting...)