Julia and others -

At our museum we have a handheld "clicker" we
purchased from a local stationary-supply store.  It
is placed near the cash register and when people
enter, we "click" them in.  Also, a sheet is nearby
and we make "dashmarks" to indicate if people are
visiting the gift shop only (no charge), school groups
(children & adults - who are charge differently than
regular visitors), "other" (like people who come to use
our bathrooms, etc. - no charge), and museum members
(no charge.)  This works quite well for us, and we get our
statistics to boot!

Just my 2"   {:-Deb

Deborah Anna Baroff, Curator of Special Collections
Museum of the Great Plains   Lawton, OK