First, the bureau isn't a blacklist. It records your payment behaviour, both positive and negative. Paying well builds history. Having no history is almost as bad as having a rough one, because the bank has nothing to score you on.
What actually moves the score
Paying on time. That's 35% of the formula. A 30-day late mark weighs for years. Paying on day 15 when the cut-off is day 1 doesn't feel good to anyone.
Not maxing your line. If your card has a 30k limit and you keep a 28k balance, the system reads it as financial stress. Keep usage under 30% of the limit — at least at statement close, because that's when it gets reported.
Account age. A five-year-old card managed well outweighs three new cards. Don't close old cards casually.
What people think helps but doesn't
Taking out several small loans «to build history» in the same quarter. Every application counts as a hard query and lowers your score. Take out two products a year max if you want to build cleanly.
Pay off and close immediately. Account age stays as long as it's open and current; closing can actually drop your score.
How to check your report
Pull your Reporte de Crédito Especial for free once a year at burodecredito.com.mx. Read through it: identity mix-ups, accounts you've closed that still show open, or late marks reported incorrectly are more common than you'd think. Disputing them in writing takes 4 to 6 weeks and is worth it.