There are many religions in the world contradicting each other and common sense dictates they can't be all true at the same time.
First you must recognize there is one true sacred book and find out which one . Such sacred book must be distinct from other sacred books and the Bible is for sure such a book.
Then you try find out which of all the christian religions is most in agreement with the Bible.And again it must be a distinctive religious group . So you can know it cannot be a main-stream religion .Main-stream religions are easy and accomodating to the world pressure to go with the main stream like most people think and do.They are religions of convenience ,not religions of thruth .Such is reality in our times .
Of all religious christian organizations ,groups the International Bible Students and after them Jehovah's Witnesses no dobut best fit to be called the true christian religions of all religious organizations.