When wearing pants, go for loose, tunic-style tops that cover your crotch and buttocks. At home, many of us like to wear our blouses neatly tucked into jeans or slacks, but here, it’s better to let them hang out. One great advantage of wearing long tops is that they hide the fact that your underwear is visible through thin fabric so you can wear lightweight pants in hot weather.
If you bring a swimsuit, it should be a conservative one, no matter where you plan to wear it; a one-piece is preferable. On the way to or from the beach or pool, or whenever you are interacting with locals, put something modest on over your swimsuit. Bikinis are not acceptable, even in Goa, where many women wear them anyway. In certain conservative locations and in many places of worship, you will also need to cover your head. Observe what the local women do, and do likewise.