wireless network

There are many things you should do first in order to get proper coverage of the area that your users will be in.

A good site survey is one, this will enable you to plan for dead spots in your wireless coverage area, i.e. setting up more than oneAccess Point.
It will also indicate where the best place is within the building to place your Access Point(s) to obtain the best coverage, this can be important for power supply to your AP, in order to get the best coverage you may need to install more than one AP and it may turn out that your AP will be no where near a power output in which case you would use an AP that uses PoE (Power over Ethernet) for example.
The site survey is one of the most important steps in deploying a wireless network, without it you could end up with a poorly perfoming wireless LAN. A good site survey will also allow you to conifgure the best power output from your AP(s) so that the LAN doesn't go outside the desired area, this will reduce the chance of outside snooping into your wireless LAN.
After the site survey you will then need to choose the most suitable AP for your needs, may be in the 2.4GHz range (802.11b) or the 5GHz range (802.11a), may need AP(s) that have antenna diversity (2 antennas), varibale power manipulation, choose between DSSS (direct Sequence Spread Spectrum) and FHSS (Frequency Hopping Spread Spectrum), then of course wireless NICs.
Lots of things you will need to consider.

If you are considering using WEP then don't make it your only source of security as it is pretty useless to tell you the truth, it's useless as a result in the way wireless frames traverse the medium (air).
If you are going to use WEP then use a server platform such as Radius to provide centralised rotation WEP encryption, include MAC filtering, firewalls etc to give you more security.