if you can work it into your daily schedule, it's best to shoot it 3 times per day at 2 iu's each time.
the reason being is that gh has a very short half life. from what i've been told it's less than 2 hours.
your natural gh levels are lowest when you wake so that is a good time for the first shot (everybody will agree) the next best time for your injection is after a work out (everybody will agree) the third best time IMO, is before bed. (not everybody will agree).
though my thinking on injections before bed is more of an old school thinking i have my reasons for this. some will say it's a waste to inject before bed. the reason being is that you're natural gh levels are highest during your 4th hour of sleep. (or whenever you reach you REM sleep). now when you're in that 4th hour of sleep, you're body is rebuilding muscle tissue as it's greatest rate. so some guys believe to let your natural gh do it's thing during that period of time and find a different time to inject the 3rd shot.
however, the amounts that you produce during the 4th hours are so small compared to the injection, i feel like taking full advantage of the period of sleep with the injection.