If the horsie doesn't I believe its down to how they were as a foal as my boy can be quite 'in your face' and he was like this from when I chose him at 2 months... people and other horses seemed to just accept it for some reason. Ive had him since 6 months but he still has to be reminded about my personal space daily- doesn't help though as my other horse (whos 17.2hh) lets him barge him all over the place!?
How its done I suppose depends alot on the horses age, background, temperement etc. As my youngster is reminded differently to my other horse who rarely needs reminding.
He can be really good, he knows to step back away from me when i take his feed into his stable till i put it down and back away then he goes to it.
On the other hand when i tie up his haynet or tighten it up then he gets a bit pushy or stands over me (his head resting on mine) to get to it. I know the easy option would be to not tie it up with him in there.
He knows 'back' and 'over' but sometimes just seems to ignore it and not listen.
He is nearly 3 and i have had him for just over a year.
Have you got Kelly Marks's book Perfect Manners? That's very good re groundwork. Also Richard Maxwell's book Birth To Backing or something like that is quite good as well.
Good for you for looking to sort this out, it will pay dividends when it comes to riding him too.
Its all about NOT letting him do it. Take a hoof pick and poke him with it if necessary. BE VERY STRICT about it. Doing the moving over/backing up exercisers daily. Also teaching him to stand still while you move right away from him in the middle of the arena etc lots of stuff like that.
AS someone else said it will very important when you come to ride him that you have this sorted out first otherwise he will think he can at best test you all the time at worst do what the hell he likes.