Credit card companies typically allowed you to accrue a few weeks of additional interest on the money you must pay to them card company by delaying payment slightly, called the grace period. Many years ago when bank interest rates were higher, that could mean a few more dollars of free money in your bank accounts.
Pay in Full
I charge pretty much everything on 2 credit cards of mine because I know that the rewards are nothing to sneeze at. I have redeemed many first class airlines tickets and cash back rewards on my the cards. It's worth charging your expenses on the credit cards with rewards if you could manage to pay the balances in full; otherwise, the 1% or 5% rewards you earn are not enough to pay for the 15% of interest charges. You'll end up losing money this way.
Credit card companies now promote their products with high rewards when the expenses incur in certain categories. They can be 5% rewards in the gas, groceries, or cell phone bills category. That is typically 4% higher than he rewards one can earn. That's extra free money waiting for you.
Buy Discounted Gift Cards
If you shop often at Target, why not buy Target's discounted gift cards online at Raise or other similar discounted gift card resellers. These gift cards can save you another 5% to 20%. One thing to caution though. Scam is very rampant in the discounted gift card reselling business. Be extra extra careful. Read the terms and conditions on the websites first. Most of them offer a buyers' protection with a short limited amount of them. Therefore, use the gift cards as soon as you get them.