This basically means whatever your dog wants, get them to ask please first. It strengthens good behaviour and means you can be training your dog without even dedicating a lot of time to it. Any time you can encourage your dog to communicate with you happily, you’re on to a winner with reliable behaviour. They learn impulse control and can consider the alternatives whilst using manners.
So what do we mean by manners? Asking them for a sit before you take the lead off (and even a wait, if you can progress to this) then reward them with a treat or play time. Try asking them for a sit before food or a toy or even to go down the garden and play. The aim of the game is to get your dog’s attention before an action and to ask them to perform a basic task they know well, you can progress this accordingly.
Some dogs sit and wait for their dinners, this can be invaluable when they come across something dangerous you need them not to eat it, then you can use a wait or leave command and reward them with something else and remove the danger. Opening a door can be an issue with certain dogs, if you always ask them for a sit before you open the door, they won’t automatically run out even if you forget one day!