Romans 14 is dedicated to this topic... Paul calls them "disputable matters" (Romans 14:1). His primary example was whether or not to eat meat, but he also alludes to the proper day of the week for Sabbath and drinking wine, all of which were wrongly believed to be essential doctrines of the time. Paul counters this, and tells us (with repetition) not to judge or show contempt for others who differ on these disputable matters:
"The one who eats everything must not treat with contempt the one who does not"
"and the one who does not eat everything must not judge the one who does"
"Who are you to judge someone elses servant?"
"Each of them should be fully convinced in their own mind."
"You, then, why do you judge your brother or sister?"
"Or why do you treat them with contempt?"
"Therefore let us stop passing judgment on one another."
"So whatever you believe about these things keep between yourself and God."
Now, we can certainly debate what is and what is not "disputable". Let me give you a few examples of what I had in mind when responding to the original post:
Calvinism vs. Arminianism (questions of predestination)
Real presence of Jesus in the Eucharist vs. symbolic representation
Different types of rapture (pre-trib, mid-trib, post-trib, etc.)
Creation questions (figurative vs. literal six days, old vs. young earth)
What happens after death (soul sleep, purgatory, straight to Heaven)
... and many others.
All of the above questions have caused division in the Church and sometimes lead to new denominations. Proponents of any of the above positions can back them up with scripture. They have been debated for centuries because Christians do not agree on the interpretation of scripture. Yes, there are may essential doctrines. But my point was that a new Christian need not become preoccupied with these hot potato debates when examining the differences in denominations.
There is plenty of room for diversity without capitulation.
Some speak in tongues and experience physical manifestations of the Holy Spirit. Some do not.
Some prefer a formal, liturgical church service or mass, some prefer an informal service.
Some cry out and "raise the roof" when praying or singing. Some prefer quiet prayer and meditation.
Diverse. All Christian. "One holy catholic and apostolic church" (which is stated in the Nicene Creed that is shared by most Christians, and part of the statement of faith of this forum).