Hi everyone! I've lurked here for a while but this is my first post.

I have the following cards:
- Amex SPG
- Citi AAdvantage Visa
- Chase Sapphire Preferred Visa Signature
- Amex Platinum (paid for by work)
- Costco Amex

I don't really know when it is appropriate (most beneficial) to use one of these. I rarely use the Amex Platinum except for getting into airport lounges since it earns me nothing; all the points go to my employer.

I use the Costco Amex at Costco and at the Costco Amex gas station. I signed up for the Citi AAdvantage when they had a 75K miles bonus, I signed up for the SPG card when there was a 30K points bonus and the Chase Sapphire when they were giving away 50K points. I've gotten all of those, and I plan to ask to speak to the respective retention departments when the time comes to fork out annual fees. I use all four (not including the Amex Platinum) for something or the other just to keep them in use.

I don't really know when and what I should use the other cards for. Help! My ultimate objective is to be like the million mile secret guy