What is the best gear to use when towing a boat with a 1999 Chevy Suburban 1500?

That truck being a rather new one might be a Z71 towing package. If it is it's at the end of your turning signal lever there is a towing button. Push the button while the truck is in nutral. Then just go in normal drive and you are ok. But if not don't worry you can just go in normal drive or you can use 1-3 gears for better fuel management. BUT you should be ok no matter what because in 1996 GM began puting Vortetch 350ci engines in most trucks witch boasts power over most full size trucks.