Use the
"selected" attribute in the option element you want to be selected by default. If you are doing this dynamically, you'll have to work it in with the code that generates the HTML for the form, e.g.
<select>
<option value="foo" ${fooSelected}>Foo</option>
<option value="bat" ${barSelected}>Bar</option>
</selected>
Above is about the crudest method, but hopefully you get the idea. BTW, if you aren't using JSP 2.0, replace the &{} with the good old <%= %>.