Learning new fitness habits is never easy, especially when a person has none. The best advice for someone who is trying to get into better shape is to start small and go from there; too much too soon is an easy road to disappoint, and that only encourages the person to give up. Obviously some changes need to be made, but those changes should be done incrementally rather than all at once.
A great example is a basic fitness regime. While everyone would love to start being an incredible athlete right off the bat, that is neither likely nor desirable; the best way to start is a little bit at first and working up from there. This means minimal weights, a few dozen push-ups and sit-ups, and maybe a lap or two around the track; you need to walk before you run, and that gives you an opportunity to learn all of the basics and become an expert in them. It also allows you to get to know your body and its limits, and how to push those limits. It also means that you can learn how to avoid harming yourself before you are ready for whatever the next stage is.
This also applies to eating as well. If you are serious about fitness, you need to make a lot of choices about which style you will follow, and that applies to eating as well. There are different diets for different lifestyles, and it is a good idea to match the diet to the lifestyle. Keep in mind that you want to avoid fad diets and only keep to diets that have definite benefits. Keep in mind also that some diets have their own limitations, such the expense associated with a true vegetarian diet. New diets take some training to get used to them, so try to keep in mind that you should be strict with the details of that diet until it becomes habit rather than training. You can then make whatever choices you see fit for your own needs.
Overall, becoming more fit is a matter of making choices and sticking with them. Do that and you should become a lot more fit in record time.