Query Strings in SharePoint 2010 - Custom Forms - SPServices

http://geekswithblogs.net/SoYouKnow/archive/2009/10/29/setting-sharepoint-form-fields-using-query-string-variables-without-using.aspx

(xizwyck)
http://social.msdn.microsoft.com/Forums/en-US/sharepointcustomization/thread/872dccfb-7b89-4076-8983-05359349cdfe/

http://splittingshares.wordpress.com/2008/04/22/defaulting-a-hidden-field-on-a-form/

LookUp Query String

<script type="text/javascript">
$(document).ready(function(){
var queryStringVals = $().SPServices.SPGetQueryString();
var IDtoGet = queryStringVals["theCID"];
var insEmail = queryStringVals["InstructorEmail"];
  $("textarea[Title$='People Picker']").val(insEmail);
  $("div[title='People Picker']").text(insEmail); }); //close doc ready
</script>

http://sharepoint.stackexchange.com/questions/17243/apply-metadata-based-on-query-string-or-selected-value-in-page-control

http://sharepoint.stackexchange.com/questions/29613/how-can-i-pass-a-parameter-via-query-string-to-populate-a-lookup-field-on-a-new

Resources: SPServices
http://spservices.codeplex.com/wikipage?title=%24%28%29.SPServices.SPGetQueryString&referringTitle=Documentation

Object Model

 string qryParameter = Page.Request.QueryString["k"].ToString();
  HttpContext.Current.Response.Redirect("Page.aspx?k=" + qryParameter);