I have done plenty of poker runs and the idea is pretty simple -

Riders pay an entry fee, which gives them an entry form to play.  Usually co-riders pay an additional price so they can also play.  A route is planned and there are designated stops along the way.  At each stop, there is someone waiting with a bag of cards.  The participant pulls a card and a person working the stop marks down on the rider's entry form what card they chose (they usually also initial the form or something too, to show that the rider was actually at the stop and not just making it up).  There might be a card drawn at the starting point, 3 stops along the route, and also a card drawn at the end, back where the ride started.  There is usually an established time for last bike out, and last bike in.  When people are return and have pulled all their cards, they hand in their entry forms, and the best hand(s) win.

Essentially, what you need to run a poker run is: a well-planned route, including stops, preferably at places that will have public restrooms and a place to get something to eat or drink - it usually is at a gas station, they usually are open to that, but get prior permission; people to man stops; several decks of cards ( usually 1 or 2 per stop); entry form you come up with.  You determine the prize, collect the money and pay the prize out of the entry fee collections.  Some rides allow riders to purchase and play multiple hands; some rides allow users to purchase additional card pulls at the end of the ride.

Other kinds of rides are bug runs, and we have even done a 'panty run' where instead of pulling cards from a bag, riders pulled numbered panties from the bags!  Hoo-boy, that was a blast!  The main thing is to have a nice route with stops, and a way of assigning points or establishing a winner at the end.