Make a floor plan, taking note of the location and composition of walls, office furniture, network and power outlets, etc.
Find out where on the plan coverage is required, and how many users will be using the access point in a each area.
Try to find out where you can put your access point(s) so that you maximise your coverage and minimise obstacles. You may want to use different kinds of antenna for certain areas. Figure 11, “Wireless Site Survey” shows you an example of what your floor plan might look like. Remember that walls may present a very thick obstacle depending on the angle the signal enters the wall.
Site your access point, pointing it in the right direction if required.
Go around with a laptop, at various places in the coverage areas. Try not to let the link quality drop below half for good results. Try putting it down on the ground, sitting down with it, placing yourself between the access point and the card, turning the computer (PCMCIA cards have a poor polar diagram, meaning at some angles, reception lulls badly.)
If you want to roam on your wireless network, you need to move around and test the handoff between access points.
Its a slow process, involving a lot of fiddly playing around, but the golden rule would be "lather, rinse, repeat". But if you only need the wireless access to access the Internet, you can be more forgiving of poorer signal quality, depending on the speed of your Internet connection.