I used to work at a family practice where we also specialized in weight loss medicine. Off the record,I don't recommend the appetite supressants (prescriptions or over the counter) most of the time (there are some circumstances, but you should be under close supervision by a medical provider) and they often have anxiety, insomnia, heart palpitations, hypertension, etc. as possible side effects. Also, the weight tends to come right back on after the pills stop.
NOW...that said, I have been a fan of the "fat-blockers" like Xenical (now OTC in a weaker version, Alli). You still have to take charge of when and how you eat, but it helps to eliminate about 1/3 of the fat calories you take in. You MUST watch your diet, or those "icky" side effects like loose oily stools, uncontrollable stools (yep, it can happen) can be really embarrassing! If you think you'll have a high fat meal due to a special occasion or a time crunch...just don't take the pill(S) that day. You can take one with each meal, up to 3 times a day. One of the benefits is, with the fear of the "ick" side effects, people tend to be more diligent of their food intake! Keep a food diary too (has been shown to be one of the best ways to lose wt. and keep it off).
Finally, don't take something like this if there's a chance of pregnancy or a plan for pregnancy in the near future. Reason? It can cause you to lose some vitamins (A, D, E, K) as they are fat soluble.
Take a multivitamin each day, preferrably not around the time you take the Alli.
All in all, it can help "boost" your weight loss while you make dietary and lifestyle changes. Just remember...it is a TOOL, not a miracle pill!