What time is your online community most active?
Is it 8am? 1pm? 6pm? Perhaps 9pm? If you run a community for insomniacs it might be 3am.
Work out what time your online community is most active and plan for stuff to happen at that time. Be active personally, organize events, initiate discussions and respond to others.
Being highly active for the hours when your community is most active is far better than moderate activity throughout the day.