According to this link,
State Towing Laws, WI by law requires trailer brakes. Is that link the definitive link for law info? No, check your states laws directly. However, know that once you cross state lines, you are obligated to abide by those states laws. Besides, there is no reason not to have properly functioning trailer brakes.
As already stated, there will be a sticker on your truck's hitch that tells you the appropriate tongue weight that hitch is rated for by the manufacturer. Should be 2 numbers, with and without WDH.
Most importantly will be how you load your TT. Make sure there is side to side loading balance and it is usually better to front/nose load the trailer to help get your proper tongue weight. Nose loading will increase your tongue weight but a trailer with less than the recommended tongue weight can result in a very uneasy tow. Here is a good example of what can happen with too light of tongue weight:
http://imgur.com/gallery/dYz2tCE
