Honestly:

Culture.

Listen to your favorite songs
Watch your favorite movies
If you don't like something -- it isn't personal preference. You just don't understand it. Realize that there is good in all culture -- it all comes from human creative impulse.
This will open your mind to all possibilities.

But this is a gradual and ever-expanding process...

If you really want the fast way:
Take shrooms. Be completely open to it and lay your ego on the table (induce an ego death)

Then go back and re-participate in culture as you've never seen it before.