As far as promotion of your blog via facebook, twitter and other social networks is concerned, I think there can't be a specific time when you have to post new content, status or something. The best you can do is to promote every new post on your blog on social networks as soon as it is posted. This can be of course very difficult and so time consuming that it may even get a little bit of annoying with time. So the best chance that you've got is to synchronize the RSS feed of your blog or website with your facebook promotion page or group, twitter account and with all your accounts on other social networks that you are using. There are special applications meant for this purpose. You will have to add the application to your promotion page and accounts. Once done, you can add the RSS feed link to the applications after which every single post that you make on your blog or website will automatically be posted on all the social networks associated with your RSS feed. If you don't know what applications I'm referring to, let me know and I'll tell you the names as I don't remember their names clearly right now.