My mexican beans consist of a bag of dried pintos soaked overnight. 1 big onion,4-5 bay leaves,2-3 cloves of garlic and about a tbs ground pepper.
Cook that over low heat until tender. (start in the morning)
My mexican rice consists of 4-5 handfuls of rice sauteed with a chopped onion, 2 cloves of garlic and a small can of jalapeno salsa. add chicken broth and cook until tender adding more broth if needed as you go. A chopped bell pepper goes in the saute sometimes too.
If you use ground beef,brown it with black pepper,cumin,powdered garlic,ground chili of choice and onion and oregano. when it is completely cooked but not browned drain the fat and repeat the seasoning to taste since alot will go away with the fat.Brown it well.
If you are using flank or ball tips or skirt or whatever rub with above spices and leave overnight.Grill and chop into small pieces. (same goes for chicken)
For hard tacos buy store bought corn tortillas or make them yourself and fry in a little oil for about a minute and fold them in half when you pull them out.salt then and open them up a little as they cool to allow for filling.
For soft tacos take the coen tortillas and place in a plastic zip bag and micro or steam until tender.
For flour add to a hot dry pan and wait ubtil puffy then flip. A little black here and there is OK for me.
I always serve with chopped cilantro/coriander and chopped onion.
Shredded lettuce and a semi hard salty crumbled cheese work well too.
Some sort of Salsa or chili sauce for extra heat is customary too.
If avacado slices are available and ripe they are always welcome as is a good tomato sliced or chopped.
Mexican food like Californian food is all about using what is fresh and good.If it out of season,find something else to use.
On edit: Burritos and tacos share the same meats but most tacos don't have rice and beans inside they have meat,sometimes cheese, lettuce tomato,hot sauce,onions cilantro. the burrito usually has rice,beans,meat,onions,cilantro,tomato.
The cilantro,tomato,raw onion can also be made as pico de gallo (a salsa) before hand and seasoned with lime, pepper,chili etc or left as garnishes.