STRAIGHT ANSWER
Am I Manglik?
Mangal dosha means Mars sits in the 1st, 2nd, 4th, 7th, 8th or 12th house counted from your lagna, stricter schools also count it from the Moon. It is a flag for marital friction, not a curse.
HOW JYOTISH ANSWERS IT
The real method, not the superstition.
Whether the dosha actually bites depends on cancellations the scare-articles skip: Mars in own or exalted sign, a benefic aspect on it, matching dosha in the partner's chart, or the dosha repeating from Moon cancel it widely. Run the check, it shows the dosha from both lagna and Moon and the classical cancellations that apply.