
Ideally any dog should be able to free-stand as it shows off good structure. I tend to work with my show dogs on a lot of foot awareness stuff by moving them around, walking them into a freestack and then rewarding when the feet are in the right place. It can be turned into a little game as well to keep the dog happy in the ring. It's also important to learn how to hand stack a dog properly and know where the feet go though, because sometimes you may be faced with a situation where you have no choice but to hand stack. I tend to bait puppies during the exam once teeth have been checked and often kneel next to the puppy so that I can easily stop them from sitting down or turning around too much.
As with most pastoral breeds, the Border Collie should be shown as naturally as possible, so definitely moved on a looser lead (obviously some tension may be necessary to keep control with a puppy but not strung up). Have seen plenty of people ruin a beautifully moving dog by stringing it up on a tight lead.
Throwing food is considered to be bad etiquette in most breeds. Treats are fine though, and if the dog responds well to them, are good for making the show ring a positive experience.