Make sure to check the sealant on the roof at least once a year (preferably twice a year) inspect for holes or small cracks that could let water in and cause expensive damage.
Do not plug your rv into a dryer outlet they may look the same but they are wired differently .I have replaced a lot of electronics for this reason.
Never leave the awning out on your rv if there is a chance of high wind or excessive rain. If it does start to rain and you roll up your awning while it's wet make sure to open it back up and let it dry to prevent mold from growing on it.
If your toilet is in the upstairs of a fifth wheel be especially careful with the amount of t.p you flush they are very prone to getting clogged .(does not make for a fun camping experience)
If your rv refrigerator is not working the first thing to do is to make sure that it is pretty level, next inspect for an ammonia smell or a yellow powdery type substance around the boiler area. (This can be inspected by removing the access door on the back outside) If either of these symptoms is present it is time for a new fridge or cooling unit.
If you do not necessarily need a fridge that works on propane as well as electric there are residential fridges that will fit most applications with little to no modifications. (usually much cheaper)