It depends on how sensitive you are to benzodiazepines (benzos, for short).
One milligram of clonazepam (klonopin) will make me sleep for a good 9 hours, but then I'm unusually sensitive... even though I was already eating valiums back when I was 15!
To be on the safe side, start low and then go up, depending oon how you feel. I would not take two 2-mg's together, instead I'd try one and then the NEXT time I take them, then do one and a half if the first experience was not satisfactory.
But this is just an example, don't take my word for it.