Preheat a skillet on medium with a splash of olive oil.I like to use a cast iron skillet. If you're using another type of skillet, you might need more oil and the cooking time may vary slightly. I like to start with a very thin layer of oil, just enough to cover the skillet, and then add more as needed while cooking.
Add all of the ingredients to the skillet. Stir to coat with oil. Cook covered for about 15-20 minutes, or until tender and lightly browned.Make sure to stir rather frequently. If it browns too quickly, add more oil and lower the temperature. If it doesn't brown quickly enough, increase the heat.Ingredients like peppers, garlic, etc. can be added in about 5 minutes before the potatoes are done for a more kick in the teeth flavor than a slow burn. Which also works well for things like spinach where you want the ingredients softened, but not cooked the entire time.
Once cooked, add salt, pepper, and any additional spices to taste and set aside.