I would like to start weight training in order to bulk up. I am not sure about how often, how long for and how hard I should be pushing myself to get the desired effects. At the moment I tend to train twice a week for 30 minutes, which usually allows me to fit in 3 exercises of 3 sets each. As for effort, I'm doing around 8 reps in each set, with a comfortable weight at first but by the third set I struggle to get past 4 reps; however I feel as though I'm only giving 70%. Also, is it detrimental to mix in cardiovascular exercises such as running or cycling?