Effective writing for a general audience, is largely the same, no matter what the topic. The most important thing you'll need to avoid is assuming that your audience knows anything about the subject of your blog.
They may be very interested in the subject of your blog, of course, but that doesn't mean that they actually know anything about it. Your job, in this case, is to make learning about the subject fun and worth doing. Good writing will be your most important ally in this effort.
Keep your writing on-topic, crisp and fun.
When you're dealing with non-experts in any field, you have to make sure that they can follow what you're saying. This means avoiding jargon, not going off on tangents and taking time to address common questions. If you remember the better teachers you had in school, you'll remember that one of the ways they made learning easier was by returning to the same topic over and over again. You can do this very skillfully in blogs and you can make it fun.
Don't assume that your audience understands you the first time you say something, be sure to reinforce it later in the text.
People find long blocks of text intimidating. When you're writing for a general audience, especially about a technical or complex topic, break it up into sections that they can digest more easily. If you want, you can use this as an excuse to do multi-part articles.
For many people, absorbing information is easier if they're given small doses and allowed some time to absorb it before they're given more information. You can also write in list format. As an example, instead of a dry topic like "Getting Malware off of your PC", you could write "7 Ways to Get Rid of Malware".
The most important thing with a general audience is not to turn them off by writing way above their level.
By keeping information simple, straightforward and on-topic, you can keep your readers engaged.
This will also help make your blog more popular, as your readers will remember that you provided them with useful information when they needed it and that it was written concisely and intelligently.
Remember to keep any beginner-level article as simple as possible. Forgo being witty, breezy or trying to show off for your audience.