In order to make your fat burner supplements work 100%, you must prioritize your fat-loss process. To start losing fat, you need to change up your diet, nutrition and calorie consumption. You need to be eating clean and to be in a calorie deficit. When going about a calorie deficit, your body has no choice but to lose fat within your body because you're consuming fewer calories/foods, and as a result, you will lose fat. With this being said, once you've understand how fat-loss works, and when you're on a steady pace of losing weight, then you can add in supplements to aid in fat-loss. Supplements are supplements; they're not needed but it'll help boost the process; in this case, it is fat-loss. So when you purchase fat-loss supplements, use it as directed, but listen to my advice to get the best results.
As intended on the bottle, you should follow their guidance, however, to maximize your fat-loss potential, I would recommend taking fat-burner supplements during your workouts. When you take fat burner supplements along with working out, you're burning 2x the calories resulting in more "fat-loss." Now let's say if you just took the supplement without working out, is it still beneficial? Sure, of course, but like I said, if you're wanting to maximize your fat-loss potential, it's ideal to take it right before your workout.
Don't take fat-burners if you feel sick, ill, or fatigued. Do not take fat-burners to think it'll completely shred off your body Fat. Fat burners do not work like that; it is to help aid in fat-loss.
When trying to lean out, don't be too lean. Having little body fat is harmful to your health; So make sure that you stick around the body fat range between 9-12%.
Now, if you were to take fat-burner supplements while having a poor diet and nutrition in place, you aren't taking this "fat-loss" protocol seriously. If your goal is to lose fat, then you should prioritize this. Eat clean, eat healthily and exercise. Taking fat-burner supplements while neglecting diet/nutrition/exercise will do little to no good. Yes, if you take it, you are going to burn calories (resulting in fat loss) however its not going to be much. That's why I said if you were to prioritize your diet/nutrition, exercise, you can efficiently promote fat-loss much easier.