I think it really depends on what your taking it for. To control appetite, or meal volume, take it 30 minutes before eating. Having food in your stomach will slow digestion, so you likely wont feel it as much, althought more may actually get absorbed to to the buffering with the food. I have used it after a big meal to keep from getting that full stomach lazy feeling.
For fat burning purposes...it probably doesn't matter too much. I've seen best results taking it first thing in the morning, about 20 minutes before empty stomach cardio, and then a follow up dosage about 4-5 hours later. For me, any later than 6:00, and I won't sleep till about 2:00.
I think the 'Y' helps with E related fat deposits, although ECA seemed to help more with hunger in my experience.
-FC