LAN/WLAN High availability

To ensure you have HA, from your access switches have one etherchannel uplink from the top stack switch and another etherchannel uplink from the bottom stack switch. 

In your wireless environment, spread your access points across all stack switches so if one switch is to fail, you haven’t lost complete wireless coverage. Position acccess points in a way to cater to this. 

Wireless controller AP migration

Recently I did a wireless AP migration from dual WLC5508 to dual WLC5520. There is not a lot of documentation out there on preference options for access points to join the controllers eg DNS, DHCP etc.
To create a pilot group on the new WLC, we were able to tell some access points to join a specific controller. In the access point High Availability options you have to specify the name of the preferred WLC and IP address.