To increase the return from your credit card, you must buy when they run any kind of offer. In my case, I applied for a new Citi Credit Card during an offer when after spending INR 30K in first 30 days would get you a INR 5000 voucher of your choice. I instantly applied for it and completed the milestone within few weeks.
After a while I forgot about it and one fine evening, an evening came through of a INR 5000 voucher. I searched about it wondering if it was a scam or not. I could figure out that CitiBank issues the voucher from same service provider and voila, when I used that for Amazon voucher, I instantly got the gift voucher code.
Amazon's INR 5000 voucher was all mine just because I could apply during the offer time. A great ROI indeed.