The point of taking the ketotifen is to keep your beta-receptors upregulated so you can run the Clenbuterol without taking time off. You can either run the Clen two weeks on, and two weeks off. Or you can take it with ketotifen and run it for a straight 6 - 8 weeks.
If you choose to use the Clen with ketotifen, take 1mg - 3mg a day depending on what works for you. There's no reason why you would need more than 1mg though. Start taking it at the end of your second week. Make sure you take the ketotifen at night because it makes you very drowsy.
Also, buy Taurine. A lot of it. It's cheap. It will help you with the Clen cramps. Take 3g - 5g per day of the Taurine.