1) Back up anything really valuable in you laptop. This is a pretty tried and tested formula but things can go wrong. A power cut at the wrong moment could really ruin your day if you haven't backed up.
2) Boot to a Live CD or Live USB drive in "try me" mode.
3) Load gparted (should be installed by default, you can apt-get it if it's not) [ Launch it using Alt+F2, and typing gparted.]
4) Resize your partitions (right click, click resize, follow the instructions).
5) Click apply and sit back while it does the job.
6) Reboot, taking out the USB stick or CD when it tells you to.
