In my house it went much smoother than I ever thought it would when we started our shoes off at the door rule. I did discuss the rule change with our kids and it wasn't overwhelming in favor of the rule change, but agreed to it nonetheless. I would catch the kids with their shoes on in the house during the first few weeks, and would just say "shoes" which was enough to get them to stop in their tracks and take them off. It definitely took about a month before the rule became a habit, this was for me included. Now I don't even think about it, it is just a habit to slip my shoes off in the garage before coming inside.
Like others have said, you will notice a difference on how clean it does keep your home. I didn't think it would be a noticeable difference, but it really is much better. Getting friends to take off their shoes when they visit may seem difficult but I think you will find most are ok slipping off their shoes when visiting. At first it was awkward to ask people to take their shoes off but I have gotten used to it now and don't have a problem doing it. Most will see you in your socks and some shoes by the door and just do it on their own anyway. If I do have to ask someone I just say "I hope you don't mind, but we are a shoes off house so we leave our shoes here by the door." No one has ever objected. I am finding that the shoes off rule is becoming more popular in my area.