The expected flow is between 600 and 1200 words per post. If the lower limit seems daunting here's a suggestion. Go to a room by yourself and talk aloud about whatever the issue is. Just reason it out. Then go back to your computer and write that up. That will be about 80% of the battle. You can do that talking in your head instead of aloud (if you have a roommate that might be the preferred approach so your sanity is not brought into question). It is very difficult to write about something without having thought about it ahead of time. On the other hand, if it is the upper limit that appears to constrain, be forewarned that you have some of the tendencies of Professor Arvan and then seriously ask yourself whether you should indulge them or put a lid on. There is no penalty in going over, with the exception that if the reader is not quite as enamored with the subject as you are, you might risk losing him.
Subject matter-wise, I will try to give you suggestions as to a general theme, but you are always free to choose another as long as you can make a good argument that it is relevant to the class. The main purposes are to get you to reconsider the recent readings, attempt to identify the gist of the arguments being made if we haven't already hit the nail on the head in class discussion, pose questions that haven't yet been answered, and especially to flesh out where your own experience speaks to the issues under consideration.
As the course progresses some of the pieces can also tie together what has come before with the current readings and also make ties with ideas/issues that are external to the course. I will occassionally comment on your posts, but not always. I encourage you to read the posts of other students and comment on them as you see fit. Some of the connections you may make are with what your classmates have written. You don't have to agree them. There is learning in giving voice to alternative views and then in trying to reconcile differences of opinion. I do ask that you treat everyone in the class with respect and do so in your comments, as you would have them do to you. The Golden Rule is a good maxim for our class.