There are services specifically for this. They charge a fee, from 2-4% (sometimes there are promos for lower fees). If you are spending to earn a bonus, e.g. 5

There are services specifically for this. They charge a fee, from 2-4% (sometimes there are promos for lower fees). If you are spending to earn a bonus, e.g. 50,000 points for spending $3,000 you are earning 16+ points per dollar (1 point is generally around 1%, sometimes better).