I have a list in a select. After selecting an option i do a check and occasionally i want to change the selected to index 0 (first option, value=""). How do i set the select to that option with jquery?

Here's an extension method that will do this so you can simplify your inline syntax

$.fn.extend({
    deselect: function() {
        this.filter("select").each(function() { 
            $("option", this)[0].selected = true;
        });
    }
});

Then, you can call it like this:

$("#selector").deselect();

Here's a demo:

jsFiddle