Use cash as much as possible. Everytime you use a card, big banks get a cut (making them richer) and your payee (local barber, shopkeeper, restaurant) lose a % of sales (making them poorer).
I get no discount for using cash unless it's someone where there is mutual trust. Then the discount is cutting out the deep pocket, short arm men...
The CC pays me 1-5% back, the above is 6% saved but very rarely. Many places won't take cash. Also the CC allows me to charge back a business that is trying to rip people off, the CC dispute process offers a fair way to deal with bad businesses without any courtroom BS where even if you win, you still lost. A judgement still requires me to enforce it.