No employee wants to exist in a vacuum. Whether they're working tirelessly to get projects done or slacking off, your workers need to know that you recognize and appreciate their efforts -- or expect them to work harder.
You don't have to hold regular meetings to share feedback, although that's one way to do it. There are many other ways to let your employees know what you're thinking -- through e-mail, phone calls, or a brief status update a couple of mornings a week.
When you do give feedback, make sure it's as clear and detailed as possible. Try to offer solutions if there is a problem. For example, don't just say, "You aren't putting in enough effort." Instead say, "When you are late 3 weeks in a row filing your budget reports, it gives me the sense that you don't have enough time invested in your accounting procedures. Can you let me know why you've been late and how we might help you get back on track with these reports?"
Don't forget to give positive feedback, too. Praise and recognition make employees feel important, which motivates them further. Take your team out to lunch to celebrate a sales milestone, get key employees gift certificates to say thanks for a job well done, or just tell them, "You did a great job on that presentation. Good work."