I always get a good laugh out of the advice given by people who have no experience and no idea what they're talking about.
Anyone who thinks clen does anything for them after more than 3 weeks of continuous usage, is experiencing the power of the mind and nothing more.
A person's beta receptors downgrade very quickly when taking clen. Generally a person's receptors will be so down regulated after 15-20 days of continuous usage that anything taken after that is completely useless.
Clen must be taken for x number of days, followed by x number of days off. Most knowledgable people go 2 days on, 2 days off, or 1 week on, 1 week off, or 2 weeks on, 2 weeks off.
No one who knows what they're doing goes more than 2 weeks on. The longer you're on, the longer you need to stay off to allow the beta receptors to up-regulate. You can't go 2 weeks on, 2 days off, that won't work.
As for dosages, that's a very individual thing. Giving out a range that starts at 100mcg and goes up from there isn't such a good idea. Some people get unacceptable increases in heart rate and hand tremors at 100mcg's. These people may do very well with 60-80mcg's.
For a first time user, start at 20mcg's and increase by 20 every day until you notice clen's effects. If you feel the effects too strongly, then the next day drop down by 20 or if the effects aren't too bad, you now have the dosage that's best for you.
Good luck,
MaxRep