NEVER! Instead, I put WT-expose' flyers inside the front covers of all the magazines in the laundromat, doctors office, etc and kept going back to check- it only takes a few weeks for the JW to find out what is happening and they stop putting out literature, I assume they decide it is better to stop leaving literature than to take a chance that apostate material will get read by the public. Of course, you have to be prepared ahead of time and have some flyers preprinted and stashed in your car. And the other option is to write, in ink- on the covers the web address of your favorite website.
added: With so many smart phones around now- writing the web addresses on the cover of the WT magazine is probably a great way to go- I better keep an updated list of my top 10 in my wallet-
Besides our JWN- please help me by listing your favorites!