Have you been denied a rewards credit card due to rules such as the Chase 5/24 rule (you have 5 new credit cards in the past 24 months)? Have a FICO score >750?
If you answered yes to these two questions, it will be worth your while to try the below methods even if you got denied. After applying online, I was denied the Chase Sapphire Reserve. A week later, the last of the three options below worked for me and I was approved with a sizeable credit line. Go figure.