Here’s what I would do. Not perfect, but a nice quick thing you can do:
(1) Determine the GI score of your carb source (eg carrots ~GI score between 92 and 101 depending on which table you look at …bad right? NO - follow along).
(2) Determine how many or what portion it would take of the carb source to get 50g of carbohydrates (eg for carrots it would take, depending on size, 7 to 10 carrots to get ~50g of carbohydrates). Chances are, if you know these limitations, the Glycemic Load, Insulin Index, Glycemic Quotient or whatever else they come up with will not tell you much more than what you can figure out with the GI and reason.
(3) Ask yourself: “How much of this carb source do I plan on eating?” If it is somewhere around a portion that would equal 50g or more of carbs, don’t eat it. If you plan on eating less or much less than a portion that would provide 50g of carbs, eat up! (eg unless your name is Bugs, chances are you will not eat 7-10 carrots in a week, let alone one sitting…so, go ahead and munch that carrot).
Of course, you could just be lazy, follow the GI charts, get bored eating and live without such great foods as carrots, corn,potatos and pumpkins. The GI is a tool and is useful, you just have to understand how it was developed and the inherent limitations in it.