Tips to improve credit score please

HeCh

"My Equifax score (free month trial started today) is only 404."

Only? I would say that's actually slightly better than most people. An Equifax/ClearScore score of 404 is towards the upper end of the 'fair' category (https://www.clearscore.com/blog/clearscore-noddle-creditexpert-whats-the-difference) and higher than the national average of 380 (as at Dec 2015, https://www.clearscore.com/blog/credit-overconfidence-costing-consumers).

If the score is important to you:
Use one of the many credit card eligibility checkers, particularly those provided by the credit card companies themselves. Ignore the interest rate/0% offers/rewards and just pick the one with best chance of a successfull application. If you get it, spend no more than 1-10% of the credit limit you are given each month. Pay in full after the statement date but before the due date.

Rothstein

Or else you will feel foolish ???