Here's how we use jQuery functions in a separate file:

// globalFunctions.js
// this should be included FIRST
// place this in the script where you want to use these functions:
// <script src="/scripts/globalFunctions.js"></script>

$(function () {

    function getBozo() {
        return "bozo";
    }

    function getUrlParameterByName(name) {
        // url = current url
        var url = window.location.href;
        var value = getParameterByName(url, name);
        return value;
    }

    function getParameterByName(url, name) {
        name = name.replace(/[\[]/, "\\\[").replace(/[\]]/, "\\\]");
        var regexS = "[\\?&]" + name + "=([^&#]*)";
        var regex = new RegExp(regexS);
        var results = regex.exec(url);

        if (results == null) {
            return "";
        }
        else {
            return decodeURIComponent(results[1].replace(/\+/g, " "));
        }
    }

    // all functions must be listed
    window.getValue = getBozo;
    window.getUrlParameterByName = getUrlParameterByName;
    window.getParameterByName = getParameterByName;
})