I think you mean 20mcg tabs. I would start at 20 or 40 mcg on the first day and ramp it up according to tolerance. Most places say to not exceed 160 mcg daily. The most effective way is to cycle 2 weeks on 2 weeks off, because unless using ketofen your receptors will be severely down regulated after about 2 weeks of use. Everyone is different when it comes to dosage tolerance, but the best advice I can give is keep an eye on blood pressure and if it gets about 150/100 drop your dosage down. I imagine at a dosage high enough to elevate you blood pressure to this level, you will be having some serious shakes.
I have a detailed write up if you want to look it up from my am space.
Good luck.