<reference name="head">
<action method="addJs"><script>jquery/jquery-1.8.1.min.js</script></action>
</reference>

<depends>
<Package_JQueryLib />
</depends>

<?xml version="1.0" encoding="UTF-8"?>
<layout>
    <default>
        <update handle="add_jquery_first" />
    </default>

    <add_jquery_first>
        <action method="addJs" block="head">
            <file>jquery/jquery-1.8.1.min.js</file>
        </action>
        <!-- or
        <reference name="head">
            <action method="addJs">
                <file>jquery/jquery-1.8.1.min.js</file>
            </action>
        </reference>
        -->
    </add_jquery_first>
</layout>

<action method="addJs">
<script>js/script.js</script>
<params/>
<sort_order>0</sort_order>
</action>