I've sold my RVs for the most money on Craigslist or RV Trader/RVT but it does take some work. If you're willing and able it will save you a ton of money over trade-in or consignment.
Cliff notes of what I've done:
Write a fairly long ad explaining the trailer and a bit about you - why you are selling, what you enjoyed about the trailer, etc. So many people just put a 10 word ad and it doesn't grab people.
Get GOOD pictures... not blurry cell phone photos. Get a wide-angled lens and some high quality pictures. 99% of the time your buyers are going to find your trailer online and the pictures are your first (and possibly only) impression.
Screen people - from the first point of contact, Google phone #s and email addresses, listen to parts of their story and be sure things add up. Ask for a copy of a driver's license and offer your to them - this weeds a lot of dirtbags out quickly.
Be realistic with pricing. At 3-4 years I've sold (quickly) my trailers at 1/2 of MSRP. At 2 years you should be able to do somewhat better but likely not much.