Hitting the gym doesn't always work for the tall, skinny guy. I worked out faithfully for years, 5 days a week, every week. All I did was high wieght, low rep workouts, and never gained a pound. I ate exactly as all the weightlifting mags told me I should, protien and carbs at the exact time according to when I worked out.
A few years doing stucco, and I've gained about 60 pounds of muscle. All I ever got from the gym was a ripped, but still skinny body.