You need to do at least 40 mins of hard CV work. I used to do 20 mins on the treadmill followed by 25 on the rowing machine EVERY NIGHT. When moving from one exercise to another try not to rest, (ie) if all the rowing machines are being used stay on the treadmill until one becomes free then get on it straight away and keep working.
I did 90 mins on the weights first before doing CV work. Triceps, traps and abs one night followed by 45 mins CV work, then Biceps, back and pecs the next night followed by 45 mins of CV work. Alternating the weight every night but doing 45 mins of CV every night.