just to add a little bit to what's been said. When i connect the trailer cord to the truck receptacle i get a message on the dash indicator (digital display at bottom of speedo) that says something like 'trailer connected'. I then squeeze the levers on the brake controller all the way together and should observe max braking action by seeing a segmented digital bar in the display go all the way across to the right. I then let go of the levers and put my foot on the brake. I should now see the digital bar go across in proportion to how hard i brake (i.e. the harder i push on the brake pedal the longer the bar gets). The '+' and '-' buttons on the brake controller are used to set the gain. Ideally you want the gain set so that neither the trailer or truck does the majority of the braking; kind of a shared effort. Hard to get it precise plus as you use the trailer and truck brakes their braking action changes (heat). I try to set my gain so that when i'm going 15-20 mph i can definitely feel trailer braking action (trailer becomes a drag on the truck). I then reduce the gain by 0.5 units and try again. If i don't feel a drag or it's minimal when braking i'll leave it there, but may adjust it while traveling depending on the braking action i'm getting. Usually though i just leave it at the original setting.