Keep your immunizations up to date
Staying mobile doesn’t matter if your laptop has a program on it designed to feed a copy of your traffic to a third party. Invest in a good antivirus/antispyware package for your machine. Most stalkers or spies won’t bother writing their own spyware to install on your machine when there are plenty of ready-made trojans present on the Internet gray market. If your computer is properly protected, it will be able to detect and isolate any known piece of malicious software, which you can then destroy at your leisure.