Visitor counting has become very hi-tech with door and gate sensors, infra-red and laser beams. But the entry count can only tell you so much. Where do visitors go after that? And which zones have the greatest 'holding power'?

We use a very simple method to find out. No laser beams are involved. Our preferred tools are a well-sharpened HB pencil (a 2B pencil works just as well) and the back of an old envelope.

We divide the site up into zones. These could be rooms in a museum, topics in an exhibition, or defined areas of an outdoor site. Then we simply count and record the number of visitors occupying each zone at a given 'snapshot' moment.

That count on its own is useless – just a random count at a random moment. But if we repeat that process to fulfil a carefully-constructed sample frame, we build up numerous snapshot counts taken at different times and on different days. That produces a robust, representative databank of visitor occupancy.

From this, we can create a 'hotspot' map of the site revealing the relative holding power of each zone.

Of course, if it's a big site, we might have to use the back of more than one envelope.

A co-founder of Morris Hargreaves McIntyre, Andrew is one of the UK’s leading authorities on...