Like any fat burner, clen will only add to the fat loss that you have created with your diet. It is a good tool, but just be aware, you won't get abs by taking it, unless you were already well on your way to having abs without it. A key to remember with clen is, the side effects are not the actual effects. When you first start taking clen, especially for the first time, you may notice some discomfort. Hand tremor is common. it can cause anxiety, effect your heart rate, as well as raise or lower your BP (it lowers mine). You may also suffer from insomnia if taken later in the day, so it's ideal to take early. I find that it doesn't take long for hand tremor and anxiety to subside, but just because you aren't feeling these things any longer does not mean that your clen isnt working.
I've seen a number of ways to take clen posted on the message boards. Everything from 2 days on, 2 days off, to 2 wks on, 2 wks off. Personally, I find that what works best for me is to take if for an expended period of time, slowly building the dose up. I would run it for no longer than 12 wks. I start with 40mcg and every 2 wks, I add 20 mcg. I will build the dose up to no higher than 120-140mcg and stay at that dose for the remainder of my time on it. When you are finished with your clen, there is no reason to tapper off.
As with a lot of the products i use, Im a fan of Geneza's clen. Its a good price and it's strong. I've used it for 2 or 3 diets now. its a good product. Just remember that it's dosed at 40mcg. Many brands are only 20mcg. So you would start with one tab per day and every 2 wks, add 1/2 additional tab. Before I started using Geneza, I had liked Oxyflux clen. I don't trust "reseach chem" clen. MCG's are a very small measurement and if they are off, they could be way off. It would be very easy to underdose it, or worse, overdose. This is one of those things that you really don't want to take too much of.