? about raising or lowering your credit score

IMO one credit card is enough for most of us. having "available" credit at the bank or better yet, the credit union, is a life's necessity. I use paypal credit for some purchases off feebay, but I make a point to pay it off by the end of the month, if I can't, I DON"T buy .. just me.
and yes I KNOW for a FACT, that ins. co. will charge a higher premium if the credit score is not high enough. FACT their reasoning is, the number crunching stat guys tell them, if you have a lower credit score, YOU are more likely to have a claim.. I say BULLSHIT. just a way to screw someone out of a few extra dollars!???
all I know is its a great feeling to know you have enough income to live and pay your bills. to not owe a c c co, anything, or bank, or have NO mortgage. but at my age ( 67) its a lot different than being a younger guy in the mainstream workforce, with a young family, etc... just me.