This falls into the category of knowing your distances - carry distances. The main thing to remember is that carry is king. You never know how a ball will roll once it lands.
That said, if you're always short, yes, take one club more. Once you're on the course, do whatever you have to do to make greens and fairways. If you can't hold a green (ie you're hitting into a green with your 4 iron), try to land just short of the green so your ball can roll up (because it will roll).
So what I would suggest is go to the range with a couple of
clubs, and note your distance. Then head to your course and note your distance with the same
clubs. If you're consistently, say, 11 yards short, then take that knowledge with you. If your 6i is good for 168 yards at the range, then you know that it'll carry 157 on the course.