Are they played at a neutral site? I ask because both conferences have a team with home field advantage.

I always thought that the League championship games are played in the location that the NFL has their super bowl's played at.

like 2015 super bowl for leagues will be played in Santa Clara , California
so on and so forth for each year.

I just took a look at the past few title games in one of my leagues and both were in neutral, apparently random cities. I mean unless the NFL has announced they'll be playing Super Bowls in Portland, OR and Columbus, OH.

Note: It may be a random city within your league since both Portland and Columbus are teams in that league.

It's a random city in your league that either is a dome or has a good chance for good weather.