Gracious Welcome - Making buyers remove their shoes as soon as they come in might make them feel unwelcome. Do whatever you can so that they feel like they belong in the home when they come through the door.
Leave Them Alone - Don't be there when it's being shown, or if you are selling yourself, don't follow them around. Let the potential buyer look around so that they can get a feel for what your home would be like for them in it.
Room Temperature - No matter what temperature is your preference, if you are selling your home, keep it at 70 degrees all year to appeal to all of those coming through to look at your home. They need to feel comfortable while they are looking.
Set the Mood - If you have a feature, make it stand out for the buyer, such as lighting a fireplace, or highlighting that beautiful bath tube with champagne and glasses. Whatever you can do to set a welcoming mood with a feature do it.
Showcase the Visuals - If you are selling in winter and have some pictures of the home during other times of the year, have those out so potential buyers can see how your home looks in all seasons. Maybe even highlight your pool or patio with some party pictures.
Light it Up - Make sure you have as many lights on as possible in the house--before it is shown. Some bulbs take a bit to warm up, so having these on and ready to go will make viewing your home easy.
Thoughtful Notes - Leaving a welcoming note may make your home stand out to a buyer.
Feed Them - Having cookies or some other snack available to a potential buyer will make them feel welcome and at home.