What? Slow down is the best advice. You have to consider how the vehicle handles the road conditions and drive accordingly. (which is a driving skill that comes with time and practice.)
Better tires, as said already, is good advice.
I dont agree with a LSD, it just helps you get sideways easier.

My Ranger with the LSD would get sideways if someone had spit on the road within the past hour.
Weight in the bed helps, to a point. Too much weight can be a problem.
To the OP:
-Make sure you have good, fresh tires, not old or dry rotted. They dont hold the road well.
-Check your tire pressures often.
-If your going to put weight in the bed, keep it between 100-200 lbs. Make sure its secured over or in front of the rear axle. You dont need a projectile if you do get in a crash.
-Slow down and be careful.