What are you suppossed to do when you are at work, after finishing all your tasks, and you have nothing else to do? Most Personnel Managers would say that you have to make your free time a productive one. I say you must take a rest, especially if yours is a very demanding job.
So, what can we do to conceal our doing nothing? I recommend the following tactics:
1. Pick up the phone: when you're doing nothing and you are able to hear your boss's footsteps down the hallway, pick up the phone and fake you're in the middle of a very important conversation. That'll give you enough time to turn around and seem busy.
2. Keep files open: when you're working with the PC, keeping several windows open will mantain the impression you're working hard while you hide your blog behind them (which is exactly what I'm doing right away).
3. Deal with old paper work: either filing all the papers you've scathered over your desk or cleaning your drawers, that gives you a good chance to relax your mind, exercise your muscles and give an impression of tidiness and commitment while keeping your mind blank.
4. Surf the web: when you work for Purchasing, Research or something related to computers, you can hide your illicit activities by opening tabs related to those products your company deals with.
These are only some options I have come across throughout my working experience. If you happen to know others, please let me know so I can seem productive while fooling around.