There are several simple steps and rules to greatly reduce the risk of browser hijacking. I can't promise that you can eliminate that risk, even if you follow all these steps.
One of the biggest factors in mitigating the risk of browser hijacking is our behavior as we browse the net. We should avoid suspicious and dangerous web sites. Many "adult" web sites, run by less scrupulous persons, open forums for uploading and downloading software and media, many eastern European and asian web sites are (unfortunately) risky. If you run one of the sites I've described, please consider before you react out of hand and condemn me for making this generalization--it's true. If you're not doing anything wrong I'm not talking about you.
If a site contains pirated software or other illegal content, it's far more likely to contain viruses, malware, and spyware.
In a work environment, have a clear policy about what web sites are appropriate to visit. Most medium-sized businesses, larger companies, and corporate enterprises have policies prohibiting visiting such web sites, and also usually have network security measures in place blocking access to these sites. Such software can't be perfect, of course.
At home, children are often less suspicious and discriminating about what links they will click, software they might run, and so forth. Parents should communicate clearly what the rules are for surfing the web, using the computer, and how to know if something "looks wrong." Parents should install parental control software when younger children are allowed to access the Internet. The newest versions of Windows, Windows Vista and Windows Live One Care, have parental control software built-in.