preworkout snack=no fat loss

if i exercise in the afternoon, would it be better not to eat anything before because i want the exercise to tap into my fat storage and eating before exercising will only burn the calories from the food?

Doesn't matter. If you have a calorie deficit, your body will use stored energy (ie, fat) to make up the deficit regardless of when you eat that snack. Think of it like this: your body needs 2000 calories daily just to maintain your current weight (for example). You consistently eat only 1500 calories (including the pre-exercise snack). Your body will use the fat stores to replace the "missing" calories, you will lose fat/weight. Once you have lost enough weight, your body will need fewer calories (say, 1900) to maintain the new weight but again, if you eat 1500, your body stil draws on fat to "fill the gap." Eventually the gap between what you need to maintain your "ideal" weight and your actual intake will get narrower and narrower, making it take longer to lose those last few pounds, but the principle will still work if you stick with it.

and if you dont have enough energy you might actually burn less calories while exercising if you dont have enough 'pep'. wouldn't you rather be able to exercise more intensely or longer?

If you are doing high intensity workout, that I think you should definitely eat something. I lose fat, and I ALWAYS make sure I eat something before I workout. Something high in carbs preferably, like a banana or bread etc. My goal is to get lean while preserving muscle. From what I have read in my own research, is that its easier for our bodies to break down muscle and protein than body fat. When your exercising, your body needs a lot of energy, quickly. If you don't eat anything, your body will start to canabolize it's own muscles. It won't run off of your fat stores.

I usually snack about an hour or so before I run or work out, maybe like a granola bar, and then something with protein in it afterwards, lately I've been liking fat free yogurt :)

If you haven't already tried it, I highly recommend fat free Fage Total greek style yogurt.  OMG -- it's so creamy and delicious -- makes eating fat free plain yogurt a real treat.  I dip strawberries in it for a treat.  90 calories, 13 grams of protein and 0 grams of fat in a 6 oz. cup -- lots more protein than regular fat free yogurt and a very creamy consistency -- tastes so rich you can't believe it's fat free.  Make sure you get the fat free though -- regular greek style yogurt has tons of fat (albeit extremely delicious).

I go with something light and nutritious - usually about 10oz of baby carrots - only 100cal and it keeps me going longer in my workout than eating nothing at all. Not only am I burning fat, I'm building muscle! =D