The best approach is the command-line utility curl. Using this tool you can submit GET and POST data easilly.
--> submit POST data
set remoteApp to "http://www.server.com/app.cgi"
set URLEncodedVars to "var1=jumbo&var2=blank%20space"
do shell script "curl -d " & URLEncodedVars & space & remoteApp
--> submit GET data
do shell script "curl [url=http://www.server.com/app.cgi?var1=a&var2=b]http://www.server.com/app.cgi?var1=a&var2=b"[/url]
You can also open the related web page in your favorite browser (your favorite browser is Safari, Internet Explorer or Omniweb) and use its built-in command to execute javascript code, which will fill and submit the form.
If you don’t know how-to do it, just ask at our BBS!