2 dell 6224 redundant best practice

With only 2 switches it is hard to say. Those switches can run in stacked mode and appear as a single switch as well as run as 2 separate switches.

If there were more switches or routers then you would use a routing protocol like OSPF and use vrrp to protect the gateway.

This though does no good if the end devices are plugged into the switch and your get a failure. This is where running them stacked sometimes is better you would bond 2 ports from a end device and plug one to each switch. (not 100% sure this model supports multichassis port bonding but I think it does).

You need to go though the list of thing you are trying to protect from. Many times it is not worth it if for example the most common point of failure like your internet can not be made redundant. A actual switch failure is very rare but it does no good to plan for that if you do not have a way to make the servers plugged into the switch tolerate the failure also.