For a little extra pzazz, you can include an inline stylesheet to control the look of your button...

<form>

<STYLE type="text/css">
input.btn {
  color:#050;
  font: bold 84% 'trebuchet ms',helvetica,sans-serif;
  background-color:#fed;
  border:1px solid;
  border-color: #696 #363 #363 #696;
}
</STYLE>
<input class="btn" onclick="window.open('YOUR_URL_GOES_HERE?tmpl=/system/app/templates/print/&showPrintDialog=1')" style="width:85px; height:25px" type="button" value="Print page" />
</form>