I agree with Mike. You'll want the trailer to be as level as possible. Weight distribution is very important too! It helps you with a smooth level ride. If your trailer is sagging it can add additional stress to the tires and tow vehicle.
An anti-sway bar or no-sway weight distribution system will help you level your trailer. One anti-sway bar system we recommend is the Andersen No-Sway Weight Distribution Hitch.
See it here: http://www.ebay.com/itm/No-Sway-Weight-Distribution-Hitch-/261422618917