This is not an area I know too much about. I personally have used a pendulum, but jokingly and not for anthing serious.

Using things such as back mirrors, crystals, water, and smoke I think are popular. You generally watch with your third eye for information, forms, etc. revealed through symbols or the gods and so forth.

Using something like a pendulum, or also using dowsing, can also be scrying. In general, you are looking for answers, solutions, or omens. Looking for something being the important part, I suppose.

But like I said, not my area sweatdrop