You know how you get an 800+ credit rating? Put all of your normal expenses on your credit card and pay it off monthly. You only accrue interest on a card if you have a balance on it that carries over. If you pay it off every month you don't.
I almost never use my debit card. Its inherently more risky because it's directly connected to your checking account. A credit card isn't. If its compromised, it's much less damaging financially and easier to reverse.
Yes and no, high utilization dings your score for the month you made the big purchase but returns to normal once it's paid off. If you routinely have high utilization CCs will just increase your limit so your normal spending is in the ideal range.
I almost never use my debit card. Its inherently more risky because it's directly connected to your checking account. A credit card isn't. If its compromised, it's much less damaging financially and easier to reverse.