As the son of two parents who grew up in L.A., and one of two brothers who spent a few years in Japan craving and trying to faithfully recreate our beloved flavour of Mexican food, I have some pretty strong opinions about tacos.
I love food that reminds me of the way food tasted when I was a kid. I love my taco shells to be made of corn tortillas, freshly fried in olive oil. I love letting the cheese, preferably a nice cheddar, melt inside as the hot oil works transforms the texture of the tortilla from dry and grainy to crispy, slightly chewy, and a bit caramelized.
In Japan, corn tortillas were so expensive, and of such poor quality, that we subsided on flour tortillas, which could only be obtained during a rare expedition to the nearest Costco. Going to Costco was almost the equivalent of making a road trip to Vegas, only better because you were certain to return feeling 10 times richer than however much you spent, and some people I knew turned a profit from going on Costco runs for others.
Meat must be prepared with the standard "taco mix", and fried with diced potatoes, minced garlic, and chopped onions. By mixing the meat with these other ingredients, you will help to stretch out the meat, but more importantly, the onions will impart sweetness, and the potatoes will add to the textural flavourscape of your tacos.
Finally, to top off the tacos, guacamole is nice. I like mine to be a simple mixture of avocado, garlic salt, lemon juice, pepper, and minced garlic.
Recently, I have decided that lettuce is to be avoided, and replaced with a 50/50 mix of chopped cilantro and green onions.
On salsa: fresh salsa, both tomato and tomatillo based are awesome. Lacking these, Tapatio, or better yet Cholula, make for good substitutes.
Tacos should be enjoyed with friends and family. This is not to say you can't enjoy a taco alone, as sometimes this is a satisfying way to eat a meal, but I find that good company brings out the full flavor, both actual and sentimental, of the taco.