90% go on credit cards (most groceries, utilities, pet supplies, entertainment, etc.). All our CCs are rewards cards, and we're careful to recognize when our Chase Freedom cards go on 5% cash back--totally exploited this when, during our wedding, there was 5% back at restaurants (our reception was at a local brewpub)! We cash in our rewards at the end of the year, and we're looking at near $700 in rewards right now, with three months to go.
Rent and phones are checks automatically cut from CapitalOne360 and sent to our landlord and family plan administrator (DH's mother), respectively. Aldi groceries are put on debit.
We occasionally have cash for cash-only purchases (hairdresser tips, cash-only restaurants, etc). Cash purchases are fairly rare.