Becoming a good snowmobile driver is a lot like becoming a good automobile driver. It takes some "dry run" instruction, some slow-speed practice and a lot of on-the-job training.
The best "road conditions" are provided by a snowfall of about 6 to 12 inches. Hard-packed or icy snow and deep powder snow make for tricky snowmobile handling. So does hard glare ice. The turn is perhaps the most important maneuver. The more you lean in the direction of the turn, the sharper you'll bring the snowmobile around. Get some help from your passenger, too. Keep enough power on to keep the machine moving. Too little throttle and you'll stall your turn.
Practice on a field, or whatever tree-free space you can find. Before starting, disengage the neutral clutch, if one is provided on your machine.
The best snowmobile drivers are those who use their machines the most. That's the way to get the feel for your snowmobile, to know exactly how it will respond in different situations and to know instinctively when to accelerate or decelerate.