Once you find the best fat burner for your goals, give it 2-3 weeks to work before you begin assessing progress or results.
But after that time, definitely track your progress to see how your goals are shaping up! Whether you take progress photos, body-part measurements, body-fat measurements, or just track your weight on a scale, you won't know if a product is helping you see results if you don't know your starting point.
That said, despite what you may think, weighing yourself more often doesn't automatically lead to better weight-loss results, as Paul Salter explains in the article "How Often Should I Weigh Myself?" Your weight is only one part of the story—not the whole story—so don't fixate too heavily on it. How you feel, how you look, and how your workouts are progressing are also crucially important!
Remember, certain people react better to certain ingredients in fat burners, so what works best for one person may not necessarily work best for another. After several weeks, if you find that you aren't seeing the results you had hoped for, consider using a different product instead.
Keep a close eye on your progress over time, stick with your nutrition and training, and use fat burners occasionally for that final 5 percent of results, and see if you can surprise yourself with what you achieve!