This should work:
<select name="title" size="1" required aria-required=”true”>
<option value="">Please Choose</option>
<option value="Mr.">Mr.</option>
<option value="Mrs.">Mrs.</option>
<option value="Miss">Miss</option>
<option value="Ms.">Ms.</option>
<option value="Dr.">Dr.</option>
<option value="Prof.">Prof.</option>
<option value="Other">Other</option>
</select>
If you have an option with a empty value as default, the required attribute works.
The required attribute is a boolean attribute. When specified, the user will be required to select a value before submitting the form.
If a select element has a required attribute specified, does not have a multiple attribute specified, and has a display size of 1; and if the value of the first option element in the select element's list of options (if any) is the empty string, and that option element's parent node is the select element (and not an optgroup element), then that option is the select element's placeholder label option.
Quoted from http://dev.w3.org/html5/spec-author-view/the-select-element.html