there are trails and there are downhill courses. the trails tend to be mostly just following the pistes down, not much fun biking-wise. the downhill courses are where it's at. some are pretty intense, some are rather tame. most can be done safely at your own pace.
a good day: start at Champery, take the telepherique up. bike down a hundred meters and then ride/push up to the top of Les Crosets (about a 1min push). ride the DH course off the right of the chairlift. it's easy and a good warmup.
in les Crosets, take the Mossettes chair lift up. follow the piste down into Les Lindarets. it's not a particularly fun trail but it gets you down where you want to be going.
Take the chair lift going right up to Chatel. ride DH course to the restaurant next to the chairlift. as you come up to the restaurant you will see where the trail continues down to the bottom of Chatel. if you liked the previous DH course, take the first right. if you want something easy, keep pedalling up the trail and it will eventually wind it's way down to the bottom.
Take the lift back up, repeat, or take the second lift back up to the top. pedal over to the Fantasticable and you will see a trail going right, back down to Les Lindarets.
once back down in Les Lindarets, take the lift going the other direction from Chatel, towards Avoriaz. at the top, go left and the piste leads you to the start of some DH courses. there are two or three that go left, and one that goes right. the one going right is easy. take it back down to les Lindarets.
once you've had enough, head back up to Switz side via Mossettes lift, and ride the big DH course down. it's pretty challenging, maybe one or two walking section depending on your skills. once down, take the other lift up back to Champery, and bike down to Champery via ski piste, road, and a cow trail.
an alternative if you like distance is to skip the DH in chatel and lindarets and bike all the way down the road from Lindarets to Montriond and up to Morzine. ride up the lift at Morzine, ride/push up to the top and over to Les Gets. Ride the DH course down into Les Gets, across the village to the Mont Chery lift. Go up, ride Mont Chery DH course. once back in the village, take the road left out of the village, it will go downhill and loop around the mountain to the right back into Morzine. Take the Super Morzine lift across (over the swimming pool area) and up. at the end of this lift is a chair lift. take it up to Avoriaz. bike the ridge line up from there towards Lindarets, there is a trail that breaks left and takes you back down into Lindarets. from there you can work your way back to Les Crosets and Champery as mentioned above.
i bike there about 10x a summer so PM me if you want to tag along for a tour sometime.