1) Always own up to buying one white lens. Once you've got one, they all look alike, so that gives you the freedom to own more.
2) When ordering from the Canon refurbished store, track the package progress and then change the delivery address to the nearest Kinkos/Fed Ex site. That way you can go and pick it up yourself without having to rush home to snag the attempted delivery notice tag off the door before someone finds it.
3) Separate checking accounts have prevented more divorces than any other innovation known to mankind.
4) You will never be able to sneak every purchase in, so build up some immunity. Do that by never, ever criticizing or questioning her when a box arrives from an online clothing, purse or shoe store. Smile. Complement her on her good taste and make a point of being pleased that she bought herself something nice. You are earning credits that you can cash in later.
5) Always include some low cost item in your purchases from B&H and Adorama – "Oh yeah, I ordered some batteries...a filter...a camera strap...etc. I don't know why they send that stuff in such a big box."
6) If you've got a big purchase planned, start the process early on. I'm going to start mentioning the new Tamron 150-600 zoom soon so that by the time Black Friday rolls around she'll be ready to tell me to just get it.
7) Never miss an occasion for a gift. A piece of jewelry tucked into an Easter Basket is also a great way to buy immunity for the future.
8 ) Ask for gift cards from your preferred photo store. "Oh that. I ordered that with the gift card you gave me last Christmas." (plus an extra $800, but who's counting)
9) Get yourself a "man cave" where you can stash all your toys. Preferably in a room she seldom goes into.
I have more, but these should be a good start.