On the subject of diet pills - I have tried them all and here are the absolute best ones:
Lipodrene - little yellow octagon pills
http://www.a-z-nutrition.com/p/1991/.html
Stimerex ES with Ephedra aka 'Black Diamonds"
http://www.nutritiondome.com/stimerex.html
Those two are by far the best I have ever used. They work like crazy. I posted the links so that you can see what they look like but I would recommend going to a small local nutrional/sport supplement store - but not GNC its too main stream. These places will have the good stuff with ephedra (dont waste your money on anything that does not have ephedra in it). The people that work at these places seem intimidating but they are usually super cool - just let them know you want to lose weight fast - but try the ones I recommended because those work for sure. Sometimes the clerks will recommend things and you get home after spending $50 bucks and it sucks and doesnt do anything for you.
What you want from a diet pill when they kick in is a light happy feeling with crazy energy. Some pills that dont work well will make you feel super full - which sucks super bad. Or they will make you feel really depressed - that sucks super bad too.
Start off by taking only one pill in the morning after you eat something (later you can start taking them without food but at first you will need to have something in your stomach). Do not take another pill for the rest of the day. Diet pills can take up to 12 hours to get out of your system so right off the bat you should stick with one pill until you build up a tolerance.
Another note about diet pills - about a half an hour to an hour after taking one you will take the biggest dump ever. Like, you will seriously feel like you just crapped out all of your insides. It has a laxative effect like that. Its actually pretty awesome.
Ok so aside from all the amazing benefits, here are some tips so that you are able to lose weight but avoid some of the side effects:
1. If you feel your heart start beating fast, lay down and breathe in and out really slowly and think calmly. You will not have a heart attack, you will be fine but you just need to relax and not psyche yourself out. These pills can make you feel like you are going a million miles a minute so sometimes you just need to take a second and calm down.
2. You have to cycle on and off. Like, take them for 3 or 4 months and then go off for two months. This way your tolerance does not build up and also gives your body a rest.
3. Do not take a pill in the afternoon unless you want to be awake all night. You will literally be tossing and turning all night.
With all that said, diet pills have helped me get amazing grades, concentrate more on work, get 10 million things done in one day and actually gave me a more positive outlook on life. If you do not abuse them and you use them to your advantage you will benefit and lose tons of weight.
Hope this information helps!! Good luck ;)