What is the best way to keep my pug's weight in check?
When owning a pug, one of the areas you can have the biggest impact on their health is by keeping them at a healthy weight.
Pugs (if for no other reason than they are so cute that they "deserve" a treat) are prone to obesity, which just like humans can cause a great deal of health problems. One way to prevent fat pugs is to only feed them twice a day a limited amount. Also feed dry dog food (which helps with tartar control and perhaps mitigates other chewing "needs") and not wet or at least not only wet food. (Besides, wet food gets into the wrinkles and other face folds, which if not removed can lead to other skin/medical problems.)
If your pug is obese or even a little overweight use the 10% rule. Cut down on how much you are feeding them by 10% for several weeks and see if they lose weight. If they are still not slimming down, then drop how much they eat by 10% again. Once the weight has come down, the amount of food can be increased slightly to establish a maintenance regimen.
Although pugs are classified as a toy breed dog, they still need exercise to help them stay fit, and it also keeps them out of a lot of trouble.
Try to take them on walks twice a day or let them run around in a fenced in backyard.
Whatever the case, be sure everyone in the household is aware of the plan and agrees to support it. The little snack from one person is a big snack if everyone gives one.
It may also be that your pug has a medical condition that needs to be treated. Some that come to mind are hypothyroidism (treatable by medication) or something that slows the process from eating to elimination (stays in the digestive system longer than "normal"). These types of things require a veterinarian to diagnose and while not the most likely/easiest to identify, may also be an issue.