Well, holding your nose and breathing is good, but just plain holding your breath is not a good RC, because it only works if you try holding your breath longer than physically possible, which is not healthy... Plus it's noticable, which defeats the purpose!

When should you RC? Whenever you go, "What just happened?!" Don't do it every hour or something because that doesn't work well. Just do it when something weird happens, so it's less habitual. Otherwise, it may work, but you're so used to it NOT working you won't do anything!