Working ahead is a good idea. Some approaches people have taken:

* 21 posts on their favorite topic

* one topic, but broken into 3 subtopics one per week

* 3 unrelated topics, each with 7 posts

* one big anchor post at the beginning of each week

* pick a list of 21+ prompts or questions and post one each day

* just making a point to post every day

* doing the friending memes, challenges, and other things that folks post during Three Weeks for Dreamwidth