I think most people are using the same type of ingredients, but for a twist I put a little vegetable oil on my tomatoes and pepper/s and put them on the grill to char. When they are black take them off and let them cool. Remove and reserve the peel of the tomato (not the peppers). Then chop the tomato (do not use the tomato juice) and add all the other goodies, garlic, cilantro, vinegar or lime juice, salt to taste, onion (can roast this too). Add chopped pieces of tomato skins for more smoky flavor.
This makes a salsa similar in flavor to Chevy's if you like that.