I sold mortgages from 2006 to 2007, during the mortgage backed securities scams, just before the crash in 2008. I worked for HSBS Bank under their HFC trademark (that they purchased a year or so earlier).
I couldn't stomach it so, I quit after 10 months.
I had to review dozens of credit reports.
We were trained to BS people into borrowing more money than they needed to increase profits for our company.
We would give them a 12% interest rate and tell them "come back in 6 months, after making timely payments and your score will go up. When their score goes up, we can rewrite your loan and give you a better rate." Of course, your credit score never goes up that fast... it was BS just to get them to sign at 12%.
We also tried to talk them into signing up for HFC Credit Cards. Any time you get a new credit card, your score drops a bit... we were told to say it won't affect your score. These scummy tactics were what made me finally quit, after 10 months.
The truth is, only Experian, Transunion and Equifax know how your score is calculated - if you visit their websites, they don't offer any guidelines for improving your score.
When you review your credit score, for example, on your credit card's website, they give you a few obscure and cryptic reasons for your score being what it is.
There are guidelines that you can follow, to improve your score but, it takes years for your score to creep up.
Someone once told me to make minimum payments (once in a while), so the credit card service could collect a fee (usually over $30)
AND 27% interest..... The person told me that this would help my credit score because, credit card companies liked making money on you.... Sounded like Urban Myth but, if it were true, is it worth the $40 to gain 1 or 2 points on your score?
When we reviewed Credit Reports, late payments were a BIG RED FLAG.
As far as a Loan Officer is concerned, early and on time are the same thing but, you're better off making your payments early.... definitely on time (by the due date).
I would suggest, getting one or two more credit cards and taking an auto loan.... and continue making your payments early.
The Credit Services like seeing multiple creditors being paid off on time, more than anything else.
My Credit Score jumped from 815 to 847, during the last three months that I had my recent car loan. Once I paid it off, my score dropped to 798.
It's voodoo math that doesn't really make sense.
BTW: I took a screenshot of my credit score at 847 to brag to my g/f

I got my first Macy's credit card back in the 80's and I made sure to never spend more than I could pay off each month.
A few times, when I took vacations, I'd put a lot on my card and I made partial payments but, I was careful to never took more than three months to pay off a credit card balance.
It takes years of being careful to raise your score 100 points.
EDITED a bunch of times for accuracy, readability and foggy memory.