Sadly, I've never been to Iran, though I would love to go. Here are a few tips for the Iranian food I've had elsewhere:
2. The choice of rice is a central decision. Get zereshk polo — barberry rice — as much as you can. Or get cherry rice, rice with pistachio, etc. All those choices are winners.
3. Lamb shank can end up being dull in a Persian restaurant. If served with dill the dish is often too dry.
4. Fesanjan, fesanjan, fesanjan. In Iceland I once ate fesenjan guillemot. The fesenjan in a can that you find in Persian groceries is actually pretty good.
5. Don't be afraid to smear mast-o-moseer (or musir; the spellings and transliterations vary, as with many of these dishes) into your rice. Always order mast-o-moseer.
6. Soups are excellent, especially if they are fragrant and have noodle-like entities. Soups without barley are usually better than soups with barley.
7. In this country Westwood, Los Angeles has the best Iranian food overall. Check out Westwood Ave. and also Pico.
8. If you are in a country where you do not expect to see Persian food, and you see Persian food, it is usually very good. As a partial exception to a rule of good eating, a single Persian restaurant can be very good even if there are not other Persian restaurants around.