It is usually best to let your estate agent show buyers around whilst you are out.  This will make the buyer feel more comfortable and they can have an open discussion about your house without fear of causing offence.  They will be able to take their time looking around and imagining themselves living in your home.

Avoid smoking and strong cooking smells prior to viewings, also if you have any pets it can be worth keeping them (and their litter trays) well out of the way whilst preparing your house for sale and during viewings.