Take them in small conditions first - I've seen guys go out in seas that were too hectic for their abilities and come in shit scared and swearing never to go downwind again!
Show them videos that show how much fun it is!
Take them in doubles - easy intro.
Downwind paddling video
Rob
Currently Epic V10 Elite, Epic V10 Double.
Previously: Swordfish S, Evo II, Carbonology Zest, Fenn Swordfish, Epic V10, Fenn Elite, Red7 Surf70 Pro, Epic V10 Sport, Genius Blu, Kayak Centre Zeplin, Fenn Mako6, Custom Kayaks ICON, Brian's Kayaks Molokai, Brian's Kayaks Wedge and several others...