and make sure you have a minimum of 10% of the GTW at the point of trailer to tow vehicle connection.
This is a MAJOR point.. 10% minimum and no more than 15% on the tongue and proper sized bars for the load EDIT Make sure the whole rig is level with the loading hitch... in MOST cases that means the top of the ball is at 19" above the ground
A level rig is a big point also Even with a walking beam suspension on the trailer, you can still over load / underload trailer tires if the trailer doesn't sit level - and 19" often satisfies that issue. .