What are some of your favourite credit card hacks? Be it cashback or miles. Mind to share?

For miles:
Add Citi Rewards and DBS Woman’s World Card to your Instarem Amaze card, then use Amaze for all purchases (except grabpay top-up, medical bills, etc. the usual exceptions). Both Citi Rewards and DBS WWC earn 4mpd for online purchases, and all purchases made with Amaze count as online (even if you use paywave in-store). Citi Rewards’s 4mpd earn rate is capped at $1k and DBS WWC is capped at $2k, which is why you might need both cards if your expenditure is higher, otherwise just one of these 2 cards is sufficient.

I always keep up to date with Milelion for more general info about the miles game, promos, tips etc.
https://milelion.com/2022/01/01/the-milelions-2...

Other than trying to optimise my spending with 4 mpd cards, I pay for all other expenses that don't earn 4 mpd with GrabPay + AMEX TCB card to earn 2.9% cashback (1.2% Grab Platinum + 1.5% cashback) :)