The rule of thumb is half of your lean body mass in grams of protein.
So, if you weigh 150 lbs and your body fat % is 25%, then you have approx 37 lbs of fat, so 150 - 37 = 113 lbs lean body mass--divide that by 2, so approx. 56 grams of protein per day. Of course this is just an estimate.
Good sources are: eggs, milk, cheese, cottage cheese, yogurt, chicken or turkey breast, pork tenderloin, lean beef, beans, nuts, soy, tofu, fish and other seafood.