Use steady momentum to carry you through rough spots like deep snow. Second or third gear is often best, since using too low of a gear can cause the tires to receive too much power, and cause them to spin. If tires start to spin, ease off the gas slightly to allow the tires to slow down and regain traction. Even SUVs gets stuck in the snow. So be prepared.
High gear is less likely to cause tire spin.
Also, floor mats, brush, rocks or tire chains can be placed to give traction in the direction of travel. The SUV can be jacked up and the holes beneath the tires filled with rocks and brush. Experienced drivers are extremely smooth. They treat every road as if it were iced. Everything is done gently.