Any exercise that decreases overall body fat. Weight training and cardio both can peel fat off the abdominal area, as well as other areas. Make it high intensity.
And lose the carbs.
Which exercise machines are good to use?
Any of them. Just get an all around workout hitting the major areas of the body: upper, lower, arms, chest, back, and legs. If you don't know how the machines work, ask a trainer. (I assume you are talking about gym equipment here.) There's not much you can do specifically to peel off the belly fat. You just need to lose body fat overall, and it'll start coming off the abdomen as well. But aerobic exercise has been shown to have a little more specificity with respect to abdominal fat. Running, walking, bicycling, swimming if you can do it hard enough and sustain it for a while. Just get your heart rate up and keep it up there for a while.
A low-carb diet does wonders for losing abdominal fat though. A lot of folks, especially women, report decreasing abdominal size after being low carb for a while. It's not only that a low- or no-carb diet will burn off body fat faster, it's that it gets rid of bloating, because eating carbs causes water retention.
Do both of these things - low-carb and regular intensive exercise - and you'll be amazed at the results. It works for pretty much everybody.