Once you've worked out how to play its a good way to get caps, here are a couple of guides its really simple once you work it out.
the first guides the best.
Spoiler http://www.gamefaqs.com/boards/959557-fallout-new-vegas/56821718
http://www.strengthgamer.com/Fallout_New_Vegas_Super_Gui.html
just remember you can use the arrow keys to move the cards to different stacks (caravans) including the other players and once its on a stack you can move it to different cards on that pack, the idea is to make a stack adding up to bettween 22 and 26 on each caravan route,
Ive read the rules, on IGN, and been able to play face cards (on my own and ringo's stack), however I can NEVER place a number card on any of my 3 stacks. if I start with a 2, I cant seem to even put a 3, 4, etc on it even off suited but the NPC does on his. I dont know if I am bugged or just over thinking the game.
Nevermind: thanks to another post, I seen you have to use the keyboard to move cards up and down as well....
thanks!