Write about things that interest you, and that you see happening around the place.
For example, if you were blogging about Toribash you may write about the new Qi purchasing, or about the Drag racer texturing event, or maybe about Rocklee2's new video, or about T3AL the new 3d artists org.
Basically you comment on things that are going on if its a blog about a certain thing.
If it's your own blog, then just put in any random things like "The phone was ringing and so I ran all the way through the house trying to find the phone, but turns out my bro playing MW2 had it sitting on his lap and didnt even notice" but you turn it in to a whole rant.
Also here is a nice mellow environment to start blogging, you wont get any real jerks. Most are just trolls that you can ignore!