#1: Write for requests that interest you. Not only are these articles already in demand, but if one person wants them, most likely others do, too. 

#2: Add the commission into your sales prices. If you want to bring home $20 for an article, don't place a price tag of $20 on the article and concede the 35% to Constant Content.

#3: Decide how you feel about "Best Offer." You have the option of also allowing buyers to make a best offer price. I have mixed feelings. On one hand, you might get to make more sales, especially with "use rights" articles that you have sold several times before. On the other hand, you might get bid down a lot more, which kind of somewhat dulls the point of authors being able to set their own prices. Making the most money on Constant Content often depends on getting this part down right.

#4: Pay attention to trends and news. With the current economic downturn it's a safe bet that economics, mortgage,
budgeting, and other similar financial articles will probably be in demand. Holiday articles may only be good for one part of the year, but if you sell the usage rights then you can re-sell the same articles to new people every year.

#5: I've found that movie reviews of recent movies (as in just released in theatres) do very well, and so do movie list articles. Book reviews have done okay for me, as well, but not nearly the same level as the movies.