When you have a computer and you use it to get online, you are a target. Simply put (and not meaning to state the obvious here), your computer is literally coming under fire by malicious code within a few seconds of logging on to the Internet, no matter what you try to do to stop it. Short of living the life of an Internet hermit (in which you simply never get online in the first place), you do not have any options as far as making yourself a completely unassailable target. However, there are some things which you can do, if you want to make yourself into the most difficult target for hackers that you can possibly be. It will not always be easy, but in time it will just turn into a habit that you rarely even think about.
For one thing, you are going to want to keep your passwords in such a way that you can just copy and paste them directly into the relevant boxes in the websites that you visit. While this might seem a little unwieldly and take a little bit more time, it will ultimately end up allowing you to circumvent the possibility of having a keystroke logger (which is a pretty common piece of malware for you to pick up) be able to acquire your passwords (so that some hacker somwhere can use them against you). But of course, you always want to do everything that you can to make sure you are not as subject to such malware even being on your system.
Do you have a firewall? If not, get one immediately. Do you have some kind of program which will allow you to sweep for malicious code that is already on your system? If not, you also need to get that. In addition to that, you would be well advised to do nothing more personal than web searches when you are on a wifi network, because they are notorious for having the worst possible security on the Internet. With these few steps, you can be a much tougher target.