1. Mandatory, regular attendance
Mind control techniques and hypnosis don't last forever. Perpetual manipulation requires perpetual renewal. That's why Coca~Cola won't let you turn around without seeing a Coca~Cola billboard. Of course, no cult could send their followers to basic training every single week for a full re-indoctrination, but they don't have to; all they need is one hour a week for refresher training.
2. Big, fancy, majestic buildings
A Catholic once told me that the reason Catholic churches are so majestic is because it helped illiterate peasants understand the majesty of the Lord. Even if that were the intention (which I'm sure it wasn't), the reality is that churches are artistic masterpieces meticulously designed to overwhelm the senses and make the viewer feel euphoric and humbled. Just standing in an empty cathedral can put you in a trance state.
If you're surrounded by images of people who made bigger sacrifices than you to the in-group and were justly rewarded then you'll feel pressure to conform with their ideology without anyone having to say a word to you. Also, your instinctively going to transfer your awe and respect for the building to the building's owner or spokesperson.
3. Hierarchical leadership
Every cult has a hierarchical leadership structure because the point of having a cult is to have followers who will revere the leaders and give them all their money. Cult leaders get people to follow them by claiming to be envoys of God. Every church does this.
Many churches won't allow you to officially join until you undergo a ritual that symbolically changes you from a member of the lost, miserable outsiders into a saved, superior member of the in-crowd. But you'll only be allowed to be a follower at the servile end of the pyramid shaped authority structure. The only way to become a leader is to either start your own cult or work your way up the ranks. This stacks the ranks with true believers who will defend the leader and give his social authority legitimacy.
4. Charismatic leaders
The biggest red flag you might be involved with a cult is if the organization revolves around a professional charismatic leader. When you go to church you'll sit down and listen to a charismatic marketer give a 45 minute infomercial. Even if everyone from the preacher to the congregation have the best intentions the end result is the same. Poor people are swindled out of their money, and the charismatic leader gets to live like a demigod surrounded by obedient followers.
5. Trance stimulation
When you enter your ornate church on Sunday morning, one of the first things that's going to happen is you're going to sing hymns with the congregation. The majestic music, combined with the majestic building and the thrill of performing an action in unison with other members of the in-crowd will work you into a trance state that will make you susceptible to hypnosis. If you're singing about being willfully obedient then you're just hypnotizing yourself, and you're hypnotizing the people standing around you listening to you sing about the virtue of willful obedience, servitude, sacrifice and faith. Even if that's not the intent, that's the outcome. Even if you don't know it's happening, it's happening. Even if everyone was forewarned and knew it was happening it would still work on some of the participants.
6. Repetitive drills and consequences for nonconformity
In addition to singing, a good cult would require its victims to perform rote physical drills like marching, dancing, kneeling or clapping. The moment you participate in a drill you're being obedient. You didn't just kneel or march or clap. You followed an order without thinking about it, and the more you do that the more likely you are to do it again. Eventually the charismatic leader won't be asking you to do calisthenics. He'll be asking for money or a favor. What's more interesting than that though. If you can get a group of people used to following your orders and acting in unison you can eventually give the whole group an order, and they'll act in unison. That would give you the power to tell a group of people to go build a house or go burn a house down.
7. Separating the in-crowd from the non believers
It's common practice for cults to tell their recruits that the world can be divided into two kinds of people: those who are inside the group and those who are outside the group. The people inside the group are always saved and admirable. The people outside the group are always lost, unworthy and detestable.
If you believe this, then you'll base your identity on your affiliation with the group, and you won't want to spend time with people whose clearer perception of reality could endanger your faith in the group.