Last I checked (which was a while ago so my count may be off, so sue me) there are 54 official major religions in the world, and each one thinks that it's the "right" religion. I say pick one that you like and stick with it.
The problem with that is that there are perhaps hundreds of different christian groups or "offshoots"; Protestant, Catholic, Presbytarian, Apostalic, etc. However, I believe that for a religion to truly call itself Christian, it has to follow the book that is the base for all these offshoots; The Bible.
For a religion to be truly Christian, they have to follow the Bible, and not just the parts they find appealing.
For example, the Bible clearly states that homosexuality is wrong. Therefore, any christian religious group that promotes or even allows homosexuality is false religion.
By doing this you can weed out several supposedly christian religions.
Then you have to take into account other religions, for example Islam and Judaism. How much do they and their offshoots follow their holy books, the Koran etc.
By looking at each religion and finding how much they follow their holy book,
and how much they use their book in teaching, you can pick out which ones are and are not right.
If you want to go deeper in finding out the right religion, look at how accurate their holy books are. Do they conflict with eachother, or contain history that is not accurate or has any error in it?
If there is a god, he would make sure there was one true religion on Earth, and the holy book that he would give to mankind would be perfect, just as he is.