Ultimate cash back

Has anyone developed a solid method for maximizing rewards and cashback on their spending?

For example, combining a great credit card with low fees and high rewards (please give me your suggestions), using apps like Karma or Reebee for cashback on online purchases, and strategically timing purchases around sales.

In this day and age, and by sharing everyone's experiences I feel like we can develop a sort of formula to avoid getting screwed over. I’d love to hear your tips and strategies