Snowy roads are definitely not fun, especially when you are in rear wheel drive vehicle. Many people just avoid doing it altogether. Many of these tips also apply to light sand and mud that might stop you from moving forward down the road.
While the ideal upgrade is obviously four wheel drive, vans with it already are expensive, and adding it to a two wheel drive van is a huge job. Here's some information to help you do it anyway, so you can continue the adventure:
Tires: Make sure you have plenty of tread. A worn tire will have far less traction in the snow. A bigger tire is ideal, because it is more surface area for traction. A trick to help increase the traction of the tire you already have is to air your tire pressure down, which will widen the contact patch. Snow tires and/or studded tires are great to use in the snow and ice, but if you are living full time in a van, switching/storing your tires twice a year might be a large task, so look for All Terrain tires instead.
Chains: Carry chains! The best way to add traction in the snow and ice is throwing these one. We use the "Z chain" style and supplement them with the rubber tension straps, which are very easy to install. Chains are also ideal for situations where you are already getting stuck.
Tools: Even when taking steps to prepare for your winter drive, it's possible you may still get stuck. Carry a shovel to dig out the tires, and sand or cat litter can be placed on the ground to add traction and melt the snow/ice a bit. Carry a tow strap rated for the weight of your van, keeping in mind the amount of force that may be applied if someone has to yank the strap with their vehicle. I have also used a piece of wood ratchet strapped to the rear tire as a cleat, just be careful not to catch your fender or a brake line.
Driving: Take it slow. If the roads are bad enough, other drivers may get impatient, but don't let it stress you. Go at your pace to stay moving and safe. Don't use any sudden increase in speed, gently accelerate to minimize the chance of slipping the tires and losing traction. Plan way ahead for braking. You don't want to stop quickly, as your tires will lock up and you will slide, especially in a corner. Pump the brakes gently and repeatedly. A great way to check the road conditions is to use your brakes slightly abrupt on a very straight section, if the nose of the van drops, you have traction. If it does not, you are sliding. In icy conditions, you may find driving in the fresh snow has more traction vs the tracks other cars have made. When going downhill, try to downshift into a lower gear and let the engine slow the vehicle down instead of using brakes.
Upgrades: A 4x4 upgrade on a van may be very expensive and very involved, but it's not totally off the table if you have money and/or are mechanically inclined. This would be the ideal situation. However, a more reasonable upgrade would be a limited slip differential. Most vans have an "open differential", which causes only one tire on the rear to spin when you lose traction. The limited slip will do the opposite, and make sure both rear tires spin in those situations.
Driving a camper van is definitely not a fun thing to do, and can be dangerous. I once slid off of a hillside and totaled a van in the snow. If you can avoid it, I recommend it. Most places you will encounter snowy roads have measures in place to plow and de-ice roads, so sometimes just parking and waiting it out is the best option. After all, you probably have a bed or couch to hang out on.
Be careful out there, and please do more research on these topics. This is just what I have experienced and learned, but others may have great advice as well.
I was inspired to write this story about a year after crashing my first van. I lost my only home and car, and it was scary not having either in just a moment of catastrophy: