Mike,
You have to be a member of the AMEX Membership Rewards program. You get points for all charges to the AMEX card. Over time they will add up and you can cash them in for all kinds of consumer goods. I bill everything I can to AMEX...utilities, cable, phones service, gas, groceries, etc. I pay off my bill once a month as AMEX does not carry a balance. The wife and I average about $4K a month in charges...but rememebr we pay everything we can using the AMEX card.
I got my 100MM EF Macro lens this way...it cost about 100K in points and "free" to me.
The current promo is for 30% off on many Canon products. The 135 L sells for $900 at Amazon.com and I can get it 126,768 points instead of the usual 181,188 points. That equates to about $300 in savings off the cash price.
I currently have 126K points in the "bank" and I am so tempted to get this lens...it would put me back to zero points but what a deal 