What are some ways I can train myself to have more discipline?

I have the biggest problem with disciplining myself. The three things that cause me the problems are smoking, eating unhealthy food, and spending money. I would like to quit smoking, lose weight, and stop spending money on things I can’t afford or do not need. And I also need to stop impulse buying. Can anyone give me advice on self discipline, or any advice one the problems with smoking or eating unhealthy food. Thanks for any advice you can give.