I drink black tea, and I can tell by smell of the quality. However, price of my chosen Hong Cha is always high.

I purchased cheap black tea in Urumqi Carrefour last Saturday, and....it's nothing special, so I'll mix it with the good quality tea.

I'm also buying Uygurs black tea bricks, which is cheap, but taste is not that good, colour is very black. I always mix it with the good quality black tea.

http://www.sevencups.com/about-tea/judging-tea/

try following the directions of the above article

By the "imported" tag.

Green tea, like black tea, is a personal choice 

go to a good tea shop, try different teas.

take your time

find your favourite

don't be pressured or hurried into buying one you don't like

Tea, like so many other things in China, is not priced according to quality, you can easily get crappy expensive tea. Get above the cheap stuff to lower the chances of getting something that will kill you, and then go try it out, find one you like.

I am a fan of puer tea. I try a sample, and I buy what I like.

The red tea is horrible to my taste..

Just buy what you like.