Mistakes to avoid when enabling IPS?

I thought I remembered having read a warning a year or so ago with regard to enabling IPS, saying that unless it's done just right one runs the risk of blocking legitimate traffic.

I was wondering if anyone could let me know whether this is correct and possibly point me toward relevant information.  I've seen guides for configuring IPS and it didn't seem too complicated but I have this nagging memory of having seen warnings about it.

Thanks,

Steve