How do I make xubuntu open programs maximised? I'm using the newest version of xubuntu.
Try the maximus package? Here's the package description:
A desktop daemon which will automatically maximise and, optionally, un-decorate windows. Has support for exclusion lists and will work with any EWMH-spec compliant window-manager.
sudo apt-get install maximus
I believe you'll need to add the maximus command to your startup programs, as it does not automatically run at boot on its own.