GR,
Mehfil is my favorite Indian place in SF, mainly because it's my neighborhood place.
I'll list a few things that are pretty tasty Indian standards w/ some pictures from Mehfil.
Apps:
Somosas are fried pastry, generally stuffed w/ potatoes and vegetables, sometimes some meat. Pakora are battered, fried vegetables. Plain cucumber salad is found in a lot of restaurants. Much better is raita, a cucumber/yogurt mixture.
Chicken:
Chicken Tikka Masala is a sort of Westernized Indian dish, said to have originated either in England or from Brits in India. It's a tender chicken breast w/ delicious creamy tomato sauce with Indian flavors, quite mild. Chicken is often referred to as something like Murgh or Murghi. Murgh Makhni or Butter Chicken is another mild and rich dish. Similar to Chicken Tikka Masala but a butter cream sauce instead of tomato sauce, again with mild Indian spices. These two dishes are pretty much my two favorites, but they are far from standard Indian home-cooking fare.
Chicken Tikka or Tandoori chicken is chicken marinated in delicious spices and then baked. It is really delicious, though by itself a little on the dry side. This is generally a little spicier, but not too much. Some restaurants will serve some other stuff tandoori style too. This chicken will often be red or orange due to the spices.
Most other chicken dishes will be curry style dishes that have less rich, but spicier sauces, and usually are dark or mixed meat. Chicken Vindaloo is a pretty popular hotter-style curry dish. This sort of dishes are much more typical of actual Indian home-cooking.
Lamb curries are also pretty common. These are generally more traditional Indian flavors, a lot of curry and cumin and saffron type flavors.
There are always tons of vegetable dishes. Potatoes (Aloo), Cauliflower (Gohbi, Cobi), Eggplant (Benghan, Bengana), Peas (Mattar), Spinach (Saag), and Tofu-like Cottage Cheese (Paneer) are standard components. Saag Paneer and Mattar Paneer are among my favorites.
Biryani is sort of the Indian version of Spanish paella or Asian fried rice. Basically rice w/ a bunch of stuff in it.
Sides
Rice, Dal (which is like lentil soup), and Naan (baked flatbread, sorta like pitas) are standard sides. I'm not a fan of Dal, don't like the taste at all. They'll often have flavored varieties of naan like garlic naan or stuffed naans. I find most all varieties of naan delicious.
That's a pretty good start to your Indian food ordering.