What is Leashing?

For blue, your top and mid should come.

For red, your mid and bot should come.

For wolves, you let the jungler hit first, then attack the wolves from range leaving them low enough for the jungler to last hit.
Same for wraiths.

Your definition of a "hard leash" is what EVERYONE should be doing.Don't leash shaco. Don't bother helping Maokai and his small camps.

DO NOT ATTACK WOLVES BEFORE THE JUNGLER.

I disagree - for a lot of champions this can be problematic, dangerous, or mana-intensive. Most of the time it's also unnecessary, and if your jungler is a slow one, it can result in you missing lane experience/gold due to minions dying before you get there. Longer leashes can also result in your jungler having to attack, move, attack, move vice simply attacking - making it not necessarily any faster.