Snowshoeing has been billed as "the sport without a learning curve". "If you can walk, you can snowshoe" is the general rule, but there are a few things that will make your initial snowshoeing forays a pleasant experience.
Begin on packed snow and level terrain. Snowshoes provide flotation, but that doesn't mean you'll be able to walk on top of deep, dry snow. By starting on packed snow you'll get the hang of it a little quicker.
Start by walking, getting used to the snowshoes on your feet. You may feel a little awkward at first but after a few steps you go from beginner to advanced intermediate.
Walk with a "normal stride width" and don't exaggerate foot lift. Avoid the tendency to walk like big-foot, think efficiency of movement.
Use a strong arm-swing for propulsion and balance. Your arms will help move you forward and keep you from losing your balance, especially if you're in powder snow.
For walkers, the addition of poles can assist you if you feel unbalanced or you are uncertain of the terrain under the snow.
If you're running, use less emphasis on toe push-off.