The most important tip I can make is to get a sedentary job that is not physically demanding. Physically demanding work and weight gain are incompatible. Not only does your work make it difficult to gain weight, but if you manage to gain weight, it'll make it more difficult to do your job.
I recently had a temporary job with the Census Bureau, and I had to stop gaining while I worked for them. The work involved a lot of walking, and I was already struggling at 260 pounds. I couldn't imagine trying to do that work while gaining more weight. I would have been miserable.
I'm now back at my sedentary office job. I have gained 23 pounds since leaving the Census Bureau, and it's so easy. I'm drinking heavy whipping cream and piling on the pounds.
If you want to gain weight, just change your lifestyle to facilitate your weight gain. Good luck!
4 years