there are a few ways, but you need to know some people just can't. someone who can see demons might not be able to see spirits. as well some people can only hear spirits, or sense spirits.
very basic thing would be to balance all your chakra's, your third eye helps with clairvoyance, but you shouldn't focus on just one, without an unobstructed flow of energy in your body, the energy can pool and cause bad things to happen in your life. with an overactive third eye you can suffer from migraines among other things.
second, certain times of the year spirits are more active, on those times, try meditating outside, or light a white candle and leave it in your window to welcome passing spirits, try communicating with them. be sure though to ask them to leave, be polite.
there's also teas and spells, as well as skrying and deviation to help you communicate with them, but the best method i know of is through meditation. perhaps if you work on strengthening your psychic abilities you could also work on speaking with spirits, i've never tried it, but it's worth a shot though.