1. You actually Work in your Office
2. You pretend to work in your Office.
I obviously, work, and at times pretend to so as well. Both are important for our survival. Most HR's will wish to bite me for telling you this concept. Trust me, it actually works!
Whenever you are in a conference room, having nothing to discuss with your team related to project work, start using multicolored markers on the white board. A person passing by will not be able to store an image of what's going on, on the board. It's human tendecy to capture BLACK and store it. Never use Black markers!
A human can decode it later which can be harmful for you in case you are writing nuisance on the board. But, multi colors cover you up.
Moreover, drawing statistical data might influence others and lay an impression that something serious is going on inside. Graph's, Venn Diagrams etc. where as, actually, in the conference room you will just be passing your time.
Roaming within the Office!
In case, you have nothing to and wish to roam about in the office and roam, people will get an impression that this guy always keeps roaming. Believe me, if you carry a printed A4 sheet along, it will serve two purposes:
1. You will be roaming freely as you wanted.
2. The formal paper in your hand will spread an impression how dedicatedly you work.