Start cautiously and find a place that has a broad, varied menu that is well loved (meaning the parking lot is always full) and most importantly, well reviewed. Wait staff with good English skills will be very helpful guiding you through the options. An actual clay tandoori oven makes a big difference with the quality of the tandoori chicken, shrimp or what have you. A sampler might be something to inquire about even if it’s not offered on-menu.
The storefront variety of Indian with all the gold and red kitkat hanging about the place usually means too heavy on the yellow curry in my experience. I have yet to encounter a variety of curry that I actually dislike, but too much to the point of heavy on the yellow is a recipe for indigestion, for me. Red curry dishes work very well for me.
Heat as far as spice is a relative thing, what is great for me may be too much for you or vice versa. Thai hot is another planet for even diehard lovers of hot food, it’s hard to describe but the usual ways of quenching the burn just don’t work for Thai hot, for whatever reason. There aren’t too many Indian dishes that you will encounter that are quite so blistering.
If you are in a metro area that has one of the “better” Indian places, nice decor, white tablecloth, wine list, etcetera spring for that to hopefully guarantee all of the above are present in one place. You’ll pay more but it will be less mysterious and less of a gamble. Once you’ve aquired a feel for not just what you like but how it is properly done, you can then venture out into the smaller or less grand places and can find yourself some good Indian food for a good price.
In my local area, an Indian restaurant that I’d consider to be in the “better” category would be Saffron Indian Cuisine, peruse the website to see if this clicks and sounds like something near you:
http://www.saffronindiancuisine.com/tandoori.htm
Water works fine with all the Indian cooking I've ever encountered.