Some will say that you should schedule your posts or tweets for a certain particular time of day, when it's scientifically proven (by data scientists) that you'll get the maximum number of page views or retweets or some other measure of progress. (Bitly says Monday between 1:00 p.m. and 3:00 p.m. Eastern is good.)
Perhaps that's true, but here's the argument for posting now rather than scheduling into the near future. If you have scheduled posts, you have to perpetually be on the alert for breaking news that will make your pre-planned messaging look inappropriate or off-key. You're also giving up any chance to engage in a spontaneous one on one conversation with someone who is listening right now.
Do you have something to say? Say it now. There's always going to be an opportunity to repeat yourself at the optimum time, and if it's good enough, you can repeat yourself over and over again. (Repetition is the very soul of the net.) Don't get so hung up on laser-targeted optimization that you miss the essence of the network as an ongoing conversation.