Saw this Singtel "Free SMS student plan" roadshow in front of Hereen last weekend.
The staff were giving out brochures and a card with a first aid sign.

I was clearing the rubbish from my pockets the same night when I realised the card had a plaster inside. On it were the words "We love Singtel free SMS" and elaboration on how free smses cause blisters.
It was a simple way to bring across the message, reinforcing the message just before the brochure is thrown away. Something more memorable rather than a card that other's would have chucked away after a second look.

I think this works well with teenagers. It'd have been even better if they had collectible plasters of different colours, try to make teenagers display them and gain more exposure for the product message.