Your chakras are always open. It's a matter of blocked or unblocked. For your 3rd eye to be open and functioning on a higher level, all of your chakras should be healthy and flowing. You can cleanse your own chakras or go to a specialist (far to overpriced, in my opinion).
Try ESP exercises, like guessing a symbol on a set of cards, and other things (Google is magick XD lol ). You can also start practicing divination, wearing certain stones (just about anything blue, preferably a deep blue like lapis lazuli), and meditating.
The more aware you are the more you will pick up on.