An essential for every stir-fry is some sort of oil, i use a little bit of olive oil.
Chop all your vegetables. Heat the oil in the pan. Add onion and any of your harder veggies i.e. carrots or cauliflower. Once those start getting tender add the slightly softer veggies like squash. Then add the meat and cook until the meat is hot. I always add the broccoli last and cook it just until it turns a bright pretty green.
I added a dash of soy sauce and garlic powder.
Serve on top of rice.