Content

As mentioned previously, blogs are all about dynamic content.
If you've taken the trouble to ensure your blog has a focus, content should follow.

Content comes in several categories:
New:

     Most-rare, this is information simply unavailable elsewhere.
     This is blog-gold.
     This is usually the hardest to make sticky.

Extended:

     This is repackaged information that is found elsewhere.
     It is how genuinely useful information stays atop the pile.
     It is also a way to ensure your own relevance.
     This is also the easiest to make sticky.
     Often this includes linking to other sites.

Referral:

     This refers to information predominantly provided by another source.
     Excellent for relevant points that do not directly tie to your blog's focus.

One last content note:
All blogs have a voice; selecting a focus for your blog gives it that voice.
Be sure to include this voice in each post (and for all content types).