I went undercover at 10 restaurants in three states to find out which spots were the germiest. The results were surprising: Visible goop didn't always translate into bad bugs, and some spotless surfaces harbored major microbes.

No matter where the germs are, how can you protect yourself if you're concerned?

1. Since restaurant seats, tables and menus can be contaminated with bacteria, order your food and then head to the restroom to wash up before eating.
2. Lather your hands for a full 20 seconds, then flip the faucet off with your forearm and open the door with your paper towel.
3. Keep in mind that you need to be more careful if you are eating finger food like a hamburger and fries at a restaurant. "Finger food" means just that: Whatever you've touched is touching your food.
4. If you need to touch your chair or handle ketchup or other condiments after washing your hands, carry a small bottle of alcohol gel hand sanitizer and use it beforehand. Experts confirm it works well.
5. Our undercover test found that half of the lemon wedges we tested had traces of human waste, making them one of the dirtiest items in a restaurant. If you don't want to give up the lemon in your drink, ask for it on the side of the glass, then squeeze the juice in and set it aside instead of dunking it.
6. Don't give up on the pleasure of dining out! Studies show more people contract food-borne illness in their own homes than at restaurants, because restaurant workers are trained in food safety, while the rest of us are not. You can learn more about cooking safely at home here.
7. If you believe you've gotten sick from eating at a restaurant, don't just take it. Report it! You can get in touch with your state's health department here.

Watch the full story on "20/20: The Real Dish" Friday at 10 p.m. ET