1. Start early
Some dick-splash, almost certainly a French ski instructor with a protectionist agenda during the snowboarding explosion of the mid-90s, started a (very effective) rumour that kids have to be eight before they can snowboard.
This is complete horse shit.
Having seen my kids pick up snowboarding within three days, aged four, I can firmly dispel any myths about needing strong back muscles, or having to learn to ski first or any other un-informed hoodoo that stops your groms shredding before they get the chance to blow out eight candles on their birthday.