I was just curious...does anyone know how many calories one should be aiming to burn while exercising? This question crossed my mind the other day and I haven't been able to find an answer!

This is just me, but I aim for at least 400 per cardio session, with a minimum of 5x/week. I usually get about 6 sessions/week for about 500 calories each=3000 calories. I manage to lose weight on this, about 2 pounds per week.

As a calorie counter, I try for a calorie deficit every day.
As long as you use more calories than you eat, you're heading in the right direction.