drink lower carb beers such as Miller LIte if you drink beer, and minimize any mixers you mix with on the weekends. I battle the same problem as well bud, and I try do do about an hour of cardio on the days I plan on drinking and try to keep my alcohol caloric consumption equal to that of the amount of cardio I do. So if I want to drink a 12 pack of Miller lite, that equates to around 36 carbs, and around 12*93-96 calories, so we'll say around 1200 calories. I try to do around 1000 calories expenditure workout, like running for an hour and weight lifting for 45 minutes.
its a challange to drink and maintain weight, if you are really worried about gaining weight, stop drinking or cut back on fast food.