when do ya add a caching layer, like

hey everyone, im curious what you all think about when to actually start thinking about adding a caching layer to your apps. weve been noticing some slowdowns when theyre busy, and while weve made queries faster and added more servers, caching seems like the next move. what stuff do you look at or what tells you its time to check out redis, memcached, or whatever. any bad experiences or regrets from jumping in too soon