How do I know it's time to start using SQL Caching on my website?

I'm running a fairly new website that heavily consists user generated content. I have read about SQL caching and I'm just wondering when you know it's time to switch over to SQL caching. The sit开发者_JAVA百科e doesn't appear to be slow or anything but It would be great to hear what sorts of signs start appearing to warn me when I should start looking into implementing it.

Profile your application - if you are experiencing performance bottlenecks accessing your database then introduce a caching layer to alleviate the pressure.

Otherwise (if you don't have any performance bottlenecks) I wouldn't do anything until a problem arises.