What Should I Do First? Weights or Cardio
This is another question I hear on a regular basis and I usually answer this by asking, " what is the goal of this workout". Are you trying to focus on strength or cardiovascular fitness today? Do you have a goal or event your training for?
My general rule is to perform the mode of exercise that will require the most intensity or difficulty first. You will have the most energy in the beginning of your workout to perform more challenging exercises.
If your focus for the day is strength or hypertrophy than perform your strength training exercises first. If you are training for a cardiovascular event than that would be the primary focus for the day.
Regardless of what you choose, don't get into a routine where you do the same thing each day.