How do you log independent restaurants calories?

For instance I went to this little mexican place today for lunch.  I have the mini steak tacos.  They are these little corn tortillas with carne asada, avocado and pico de gallo.  I also had a little refried beans.  How do you long this?  It isn't a chain restaurant so its not in the database.  I can't find anything close.  Do I do it separately?  What about the way they cook it?  I am sure there is more calories than just logging it by itself.  Please advise...

I just take my best stab at estimating it -- 2 small corn tortillas (or whatever I ate), 4 ounces of beef (it it looked like a deck of cards, or less if it looked smaller), 1 teaspoon oil, 1/4 cup avocado (or whatever it looked like), 1/4 cup salsa (or whatever).  I don't eat out that often, but can usually get in the ballpark from all my practice weighing and measuring at home.

I also differentiate between "routine" eating and "special treat" eating.  Usually, for me, eating out is a "special treat", and on those days I usually aim for maintenance calories rather than weight loss calories.  But I try to keep "special treat" occasions to less than once per week, so sometimes I try extra hard in restaurants to make lower calorie choices and control portions so that I don't "waste" a special treat on something ordinary.

Thank you so much for your help. That is what I was pretty much doing, but I wasn't sure about seasonings, butter Vs. oil, etc....  But at least I have something to go on.