Strategies To Lose Weight Fast

I’m trying to get in shape in the summer and I want to lose weight safely, but I was just wondering about how much weight that could be over a 3 month period? I know not everyone has the same metabolism, nor do they follow the same diet/workout routine, but I’m just curious if anyone knows around how much weight should I expect to lose, say following Weight Watchers or plans similar in their goal of changing your eating habits?