I like to get at least 10 minutes in after lifting with the heart rate above 150, 30 if i'm feeling froggy. Plyos, dumbbell cleans, jumping rope, burpees etc all with a short break in between. For machines i prefer the stairmaster, i'm usually dripping sweat on every step after 10. It isn't for everyone but it works for me as my goals are to train for endurance as well as strength. Dylan an Steve have some good opinions on cardio.
You will hear a lot about fasted cardio in the morning as well. Try a search, it's one of the most popular topics on here, the ole "how can i burn fat while preserving muscle" thing.