What do you say, that before getting serious, we start with your description of how you're cooking the orzo? Along with some information recounting how much sticks and when you notice it?
As a threshold FYI, like most pastas orzo is usually cooked in plenty of liquid (water, court boullion, stock, etc.), so much so that the orzo is drained when finished. As a rule, it is not cooked like rice -- i.e., with the exact amount of liquid necessary to hydrate.
I put 2 cups of orzo with about 8 cups water and plenty of salt. I cook it for about 8 minutes. When I drain it out there is always a bit of orzo sticking to the bottom of the pan. I than rinse it off with cold water to stop the cooking process.
Like any other pasta, it needs to be stirred from time to time during the cooking. The key to boiling any pasta is to use lots of water and to make sure that the pasta keeps moving around in the water.
That said, you may be doing it right. But when you pour it out of the pot into a colander to drain, very often a few pieces will stick to the pot. Nothing you can do about that, just pluck them off or rinse them off with cold water, esp. if you are going to rinse the whole mess of pasta anyway. Although I am not a fan of rinsing pasta if I am then going to sauce it and serve it hot right away. Just drain, add to the sauce, toss, and serve.
Nothing. You're not doing anything wrong. You've just run into a "that's the way it is" situation.
You can try adding a little oil to the cooking liquid, about 2 tbs to your 1 gallon. Italian nanas swear by it, while on the other hand it's an article of faith among professional cooks that it does nothing. Try it, what can it hurt?
Stir the orzo a few times during the cooking process, to make sure everything shifts and nothing cooks on to the bottom of the pan.
Drain the orzo into a colander or other drainer, then use a metal spoon to get what's left and willing to come out easily. If there are still some unpersuadable orzo grains, put some liquid in the bottom of the pan to soak whatever's left off and make it easier to clean after dinner.