I think you might be looking for something like this: $("select:first").focus();

Here is the JQuery code:

$(document).ready(function(){
    $("#myBtn").click(function(){
        $("#myModal").modal();
    });

  $('.modal').on('shown.bs.modal', function () {
    //$(this).find('input:text:visible:first').focus();
    $("select:first").focus();
  })

});

When you run it you can see the select box is highlighted blue (at least in Chrome it is) I found this answer based on a similar question. Hope that helps

EDIT:

If you want it to select either the first text or select field you can use:

$(this).find('input[type=text],textarea,select').filter(':visible:first').focus();

If you need it to look for additional input fields (like password or radio button) you will need to add them in the find list. Another similar question asked here.

Here's my solution developed on top of that by @craztmatt and others. I have extended to have the selection of the target element start at the modal that triggered the event.

// do this to make bootstrap modals auto-focus.
// delegate to body so that we only have to set it up once.
$('body').on('shown.bs.modal', function (e) {
    var ele = $(e.target).find('input[type=text],textarea,select').filter(':visible:first'); // find the first input on the bs modal
    if (ele) {ele.focus();} // if we found one then set focus.
})