Winchester Laser

What is the best way to set up a Winchester 1300 shotgun with a laser/ flashlight combo?

I would like to be able to switch these on & off by the trigger guard area. I have read about the picatinny rails and am unsure what these are about.

One solution

http://www.gunbroker.com/Auction/ViewItem.asp?Item=117155049

or

http://www.gunbroker.com/Auction/ViewItem.asp?Item=117310154

or

http://www.gunbroker.com/Auction/ViewItem.asp?Item=117261030

22lr RIMFIRE RIFLE SHOOTING HIGH VELOCITY WINCHESTER LASER AMMO REVIEW