Don't split your clen dosage, the half-life lasts too long. Take it at the same time each day, and gradually increase, until the side effects are too much. Also supplement with plenty of water, and if you start to cramp add Taurine and/or Potassium (Bananas).
I always start around 20-30mcg, and slowly increase, until I get up to around 140mcg by the last 2 days of the 14 day (2 week) cycle. There is no point to taper down with Clen.
Then 2 weeks off and 2 weeks on again. During the off weeks you can also take Benadryl (Tylenol PM -- same thing) at night when you sleep to help clear your receptors. DO NOT TAKE ANYTHING CONTAINING DIPHENHYDRAMINE -- tylenol pm, benadryl, etc.(sp) WHILE ON THE CLEN!