1. Don't personalize your RV too much.
Changing furniture or fabrics, such as curtains, makes it harder to sell the RV, since everyone has different taste. The manufacturers choose fixtures and decor that appeal to the largest audiences, so when trading that trailer or motorhome in, the dealership loves to see original fixtures in great condition. If a unit has had modifications made, the jobs need to have a professional finish, so that the modification looks like it was part of the original design.
2. Do keep records of upgrades and point them out.
If you had solar panels, larger holding tanks, or a generator installed, do keep records and share with the dealership. If upgrades like this are done professionally and within the weight rating of the unit, they can add value to your trade-in amount.
3. Don't wait too long.
RVs take a lot of abuse as they fly down the freeway or vibrate over gravel and dirt roads. Beside that, we track dirt and sand in (seems like you can never get all the sand out, no matter how much you vacuum, right?), spills happen, pets and kids happen, and things break. The longer you have the unit, the more the wear and tear shows.
The key is to consider from the time you make the purchase whether it's possible that you might trade-in your RV. If so, consider this list before bringing in custom furniture or switching out the blinds for pink mermaid curtains.