When planning for a a wireless deployment consider the following points in formulating your plan.
1) Will your solution use Standalone Access Points (AP's) or be a Controller-based solution using Lightweight Access Points (LAP's)?
Standalone AP's - Operate independently, have standalone IOS on board, are configured directly on the AP, can be managed via Wireless LAN Solution Engine (WLSE) and redundancy is offered by deploying multiple AP's.
Controller-Based AP's - Are dependent on a Wireless LAN Controller (WLC), IOS is delivered to the LAP via the WLC, configurations are applied from the WLC, management is via the WLC, and redundancy is provided by the deployment of multiple WLC's.
2) Collect information on the required switch ports to connect your AP's and WLC or WLSE
3) Check the local infrastructure to make sure the new WLAN solution can be implemented, this will include monitoring available bandwidth.
4) Set out a plan for the additional equipment required.
5) Plan your implementation, to include where you intend to locate the AP's, the configuration of the AP's/WLC, necessary configuration of the switch ports (do you require trunks for Standalone AP's or an access port for a LAP?).
6) Develop a plan to test your new WLAN solution which could include check points such as does the client get an IP address? Can the management devices reach the AP's or WLC? Can the WLC reach the RADIUS server (for authentication).
With the information gathered from the points above you should be able to formulate a suitable plan that can be deployed and verified.