Tires, Tires, Tires
Get good tires for the trailer, I have been using GoodYear Endurance, they track well, wear well, US made, good quality.
Pay attention to your tire pressures. Should be a sticker on the trailer somewhere.
Watch the wear on the tires. If you start to see an edge wear, you have a problem to look at.
Consider a tire minder set, but not necessary.
Check your spare and make sure it is not flat
Trailers sit a lot, so the tires get a different abuse than car tires. Check the date code on your tires, every 4-5 years, I would replace them. I do.