Any good advice on churning cards?

I'm mostly interested just in Amex MR points. I use a Preferred Rewards Gold as my main card, and I have had a Business Open in my name and also in my father's name. I have a Platinum card in my name, and will cancel that shortly and open one for my wife (she is the one who really uses the travel benefits anyway). She has not has a USA-based Amex card in her own name until now.

I spend about $25K a year, so I can easily spend $1-$3K in 3 months, but making $10K in 5 months (as for some of the business cards) is something I can do, but not repeatedly.