Coyotes just like any other mammals have an excellent sense of smell. You can use this to your advantage when you are coyote hunting. However, it could also ruin your hunt if the coyote gets a scent of something he doesn't like. There are two important concepts here, attracting scent and cover scent.
There are a couple of things you can do to keep the coyotes from getting a whiff of your body scent, and trust me, you don't want this. The most important thing is to always position yourself downwind of the coyotes. This is the best defense over any scent killer. The hard part is deciding where the coyotes will come from. It has been my experience that they usually come from the opposite side of human activity. If you are hunting near a road, put the road at your back. If there are houses nearby, the coyotes will probably come from the opposite direction of the houses. If you're out in the middle of nowhere away from anything resembling civilization, find a field and sit downwind in that field. At least you will know that any coyotes coming into the field will not get your scent.
Cover scents should also be used. You can find scent killer at any outdoor store, and Walmart usually carries it as well. To put it bluntly, scent killer products make you smell like dirt. They have an earth like smell to it and it does a pretty good job of covering your smell, given that you don't just reek of something abnormal. There are also scent killing soaps and laundry detergents if you are really paranoid about your scent. Theoretically, if you take a shower with scent killing soap, wash your clothes with scent killing detergent, and use the spray before you get in the field, your should be good to go. Personally I don't go this far with it, I just use the scent killer spray and position myself downwind of where I think the coyotes will be.
Using scents to attract coyotes is also an excellent way to improve your coyote hunting results. Some scents you can use for this is the urine of bobcats, fox, and rabbits. You can find all kinds of people out there who believe in one over the other, probably because they had a good or bad experience at one time or another with a particular scent and now bash it. My recommendation for you is to use all of them and see what works best for you.
There are a couple of ways to use the scent. You can buy scent releasing products that will release the scent for you. An example of this is scent bombs. Just spray the scent on the scent bomb and hang it from a tree limb. Another way that is popular is to apply some scent in a few places around your hunting spot. It is urine, so make it as if the animal was marking their spot. Just try different methods and remember the one that works the best.