Training dog to hold command until released

After reading through a lot of the posts on here I would like to teach our lab to hold a sit/stay/bed until he is released. We have apparently trained him that he needs to do the command but doesn't need to hold it - I know it will be something straightforward but just wanted a bit of advice on how to train it?

The main one is "bed" when visitors come, I want him to stay there until I tell him its okay to come.

I honestly think he spends his days training us

Thanks,

Dave

Its common that dogs get used to - do the action, get the treat - game over
and thats usually our fault cos most of the time thats what we do - not give them any further guidance after the reward for the action

I dont use a 'stay' command I just get the sit/whatever then feed several treats while they are still in the position (quickly so he dosent have a chance to get up) then give my release word (I use 'OK') and lure them out of the position
repeate but leave a slight gap between a couple of the treats - release
build up the gap between treats
Then once the dog has got the game slowly add movment - if the dog gets up you have gone too far - sometimes just move your hand 1/2 an inch from your dogs face - then right back and reward before they move
Build up slowly to you standing up, moving your weight back, taking a step back, a side step, a couple of steps, walking to a chair, hovering your bum over the chair, sitting in the chair
then once they are solid with everything you can do add other people and other distractions

Thanks for the advice Ben, we'll get started on that today, I wasn't quite sure what to do for the release and using ok is a good one.

I was actually born in paisley at the RAH!

what a small world