Christians (and other religious people): How do you distinguish a religion from a cult?

Some mad man comes up with all of these followers and makes these crazy promises that if they follow him, their lives will be better. The small crowd of say, 12, becomes 100, then a thousand, then a million. Does this sound familiar? Jesus Christ telling his disciples to follow him to salvation? or crazy cult founder finding 12 homeless bums off the street and telling them to drink the punch (which would be poisoned) and then they will be saved forever and ever. Christianity, and any religion, is just a glorified cult, and the blind sheep followers are blind to the truth, or the proverbial "light." of the truth. They cannot decide for themselves. The similarities between religion and cult are endless. Now what are the actual differences?