i really like using the straight ECA, first because it is cheaper and i believe it to work better than xanedrine or hydroxycut. As for use i would suggest between 20-30mg/200mg caffein/200mg Asprin 30-45min before your workout. if you decide to take the ECA with a meal, takeit atleast 10min before eating.
A good ECA stack should be taken 3 times per day(Breakfast, midmorning, lunch or mid afternoon).