The key to an effective presence on social media sites like Facebook and Twitter is to consistently post new content. The key to getting that content read is to post it at the proper time. Unless you know the best time to post the only thing you can do is post all the time.
There is a solution to this.
I just published this video tutorial that describes Buffer. An web application that allows you to schedule posts to Twitter and Facebook. When scheduled, Buffer takes the guess work out of the best time to publish the posts.
Using Buffer and following my Twitter posting strategy you will be able to keep your Twitter feed topped off without spending all of your time doing it.