I would suggest taking clenbuterol in the morning as opposed to before your workout. For one, you want to have a increased metabolism throughout the day so you'll be burning fat even if youre at work. Also, if you take clen too late it could effect your sleeping. As for cardio, 30 minutes sounds fine. Personally I never do more than 20 minutes. But remember to keep your cardio moderate, and not too intense. Your heart is already working extra hard on clen and you dont want to do over do it.