Start very slowly and ramp-up. If I remember correctly you can start with as little as 20 micrograms/day. Do not do too much too fast or you'll be a twitchy, sweaty mess.
Clen has a very long half-life. Don't take any after lunch (I sure can't).
Do it in 2-3 week cycles unless you are also taking Ketotofin (sp... look it up). Your receptors get saturated and you lose the benefit of the drug otherwise. Also, I personally don't think you should do the Clen/Keto in one bottle. Instead, take your Clen ALL pre lunch. Then take ALL your Keto before bed. It makes you hungry and it made me sleepy as well. Worked best that way for me because it crashed me right out in the evenings.
Clen for the first 5-7 days was reported to be both an anti-catabolic and a thermogenic stimulant. After the first week or so it becomes more of a stimulant I think.
My info may be dated though... there may be better, more current knowledge out there.
Be careful with that stuff and don't OD.