1) Do you need Java?
If not, uninstall it complete. If you're not sure, well, you're probably not a techy user - no fret, and it's not meant as a derogatory term - simply as a matter of fact (and count yourself blessed).
2) Which browser do you use?
If you're on Chrome, be sure to turn on the "click to play" feature. If you're not, you should disable the following plugins entirely in your primary browser, and use a secondary browser (like Chrome) for the few sites that require the aforementioned: Java, Flash, Adobe PDF.
Those two points are un-negotiable.
After that comes a lot of possible ways to harden your online experience, which are optional. But the two above, currently, aren't.