If youre doing a fat burning stack at all, I would only really suggest doing an ECA stack(ephedrine,
caffeine, aspirin). Stacking two
fat burners together could lead to a number of side effects that you are definitely trying to avoid.
ECA
This combination is the revolution of dieting. They are
thermogenics (substances that increase blood-pressure by narrowing the veins in the body, resulting in more heat production and more
energy use as a direct consequence) with and incredible synergistic effect. Ask anyone in the business and they will tell you there is nothing better for dieting down. It's top of the line. Every company has its own ECA fat-burner. A lot of people have a problem with ephedrine-containing products, because it can be a dangerous substance. It's illegal in some countries, and in most countries if more than a certain amount is sold at once. Ephedrine is perfectly safe for a healthy individual, but as you no doubt derived from the previous, anyone with and already high blood pressure or with cardiac problems could seriously aggravate the condition. This could be lethal. And even in those healthy people large doses can be life-threatening. But to this day, I have yet to come across any weight-loss product containing more than a tenth of the potential dangerous amount per dose. A little insider trick is to replace ephedrine with its herbal alternative Ma Huang. It's structurally the same compound, slightly weaker, but with a very similar effect. It's also standardized for ephedra alkaloids so the doses are adapted to the means.
Also some people have adverse effects from ephedrine or similar substances. And not a few people will get the jitters from it, and most likely at some point during your stack you will experience a couple of nights of sleeplessness. They are very stimulating compounds, all three of them. This makes for
one beneficial side-effect though, and that's added
vigor in your workouts. Ephedrine and
caffeine are also popular ingredients for
pre-workout energy stacks. Should you find that jitters or sleeplessness make your life rather difficult, try cutting back the dose. And avoid using it close to bedtime. The best advice I can give as far as this is concerned is to consider it a pre-workout stack, and use your last dose prior to a late workout, so you get it out of your system by the time you get home. That should solve the problem for most. I'm not going to get into the doses, most of the fatburners are pre-stacked and they are the only products where you can rely on the prescribed dosage. I advise you to follow the directions. If however, problems remain or you really have a low tolerance for ephedrine, it may be time to consider an ECA free stack.
ECA stacks should be taken at a rate of 175 to 250 mg of
caffeine (or 900-1100 mg of guarana), 60-90 mg of ephedrine (400-550 mg of ma huang) and 15 mg of the aspirin ingredient (usually salicin). In actual life this is of little use, since noone these days buys all three ingredients separately, so you are at the mercy of the producer of the stack. Taking it 3 times a day seems to be the standard recommendation, and considering you will be eating at least 3 actual meals daily, that's not such a bad idea. You take it about 30 minutes before your meal, this will increase
thermogenics and suppress appetite. Another good way of using it, is as a pre-workout stack (I'm not a
big fan of those because I believe they aren't really worth the money). Taking them before a workout will
energize a potentially bad workout and salvage it. The thing is, the ingredients are basically the same as most pre-workout energizers.
Source:
http://www.bodybuilding.com/fun/catfat.htm 
Lipo-6 and Hydroxycut together??, Can these two be stacked?
