First and foremost make sure your tires have a decent amount of tread left (>6/32'nds) and that they are decent all-terrain tires. Since its a 4runner it should have all-terrain tires on it already.
Make sure your 4WD works. Spend some time getting familiar with the system like how to shift into and out of 4WD. Read your owner's manual regarding what types of conditions to engage 4WD and how fast and far to drive with it engaged.
If you plan on driving in deep snow, take a small snow shovel and tow straps. Also, make sure you have a car charger for your cell phone. Make sure you top off your washer fluid reservoir before you leave and that all of your lights are working, including hazards, tail lights, and brake lights.
The hardest part about driving in the snow is recognizing the road conditions. I can't tell you how many times I've almost rear ended someone driving 20 mph on wet roads when they think they're icy. If the road looks wet and its above ~35 degrees most likely traction will be the same as any other rainy day. If the road looks wet and its below freezing, use caution. Most likely there will be patches of ice on the road if its not well maintained. If the road is snowpacked and its right around freezing then this will be one of the slickest conditions to drive in. If the road is snowpacked and the temp is below ~20 degrees then the road will offer decent traction, but still use caution. Road conditions can change almost instantly too, so use caution when driving up and down mountain passes, as the roads are most likely worse near the top.
When driving on slick roads the best thing to do is drive a speed you are comfortable with, but not so much slower than traffic that you yourself become a road hazard. Give yourself plenty of stopping room from the person in front of you. Don't make any sudden maneuvers like swerving, punching the gas or panic stopping. Imagine two strings tied to the bottom of the steering wheel with the other end of one string tied to the brake pedal and the end of the other string tied to the gas pedal. While the steering wheel is straight and neither pedal is depressed there is a little slack in each string, but if you are turning the strings become taut, not allowing you to press either of the pedals much, just enough to slow or speed up gently. The same for if you are slowing down. If you press the brake pedal, the string will not allow you to turn the wheel much, just enough to steer out of a lane. What this method does is eliminates too much input to the wheels on slippery roads which cause them to break traction and skid.
Other than that, just drive how you feel comfortable. If visibility or road conditions become too much of an issue to continue then pull over and wait it out.
Hope this helps...
