1) Don't Ever Convince: You don't ever be the one who is "carrying" the relationship or trying to convince him to want something else/more with you. Doing this is one of the most dangerous TRAPS women fall into with men and relationships. If you avoid ever being the one who's trying to lead and move things towards a real commitment, then you'll never have to guess if the man in your life is genuinely interested, ready and personally devoted and inspired.
2) Give Him His Freedom/Make Sure It's His Idea Too: You tell him what you want, but you don't demand it from him. A man can't and won't commit for the long term just because a woman gave him an ultimatum. It also has to be HIS IDEA. By letting a man know that you want/expect a committed relationship if you're going to spend time and really open up and share yourself with a man, but that he has the FREEDOM to say and feel how he really feels... you leave space for a man to make his own choice and commit himself to you. This is the important process of a man becoming DEVOTED to a woman, and if you don't leave space to know how he feels and for him to come towards you and ask for and want a commitment, he won't become devoted to you in the same lasting and bonded way.
3) You Listen to Him: A man will generally let you know if he wants to be with just you by his actions, and how often he wants to spend time with you. If he wants to spend most of his free time with you, and looks to make plans with you 3-4 times a week or more, he's probably thinking "commitment" with you. But too many women spend time with a man Physically and Socially 2 or less times a week and think that this time and intimacy means that he must want more. Most men could do on "casually" dating a woman, or several women, for months at a time and never spend more than 1 night or so a week with them, and never think about or want a more serious relationship to come of it.
Also, lots of women don't listen to what a man has said about what he wants and where he's at in his love life. If a man said to you when you started dating "I'm not really looking for a relationship right now", but you're spending all your time together, it doesn't mean that he's changed his mind and wants a long-term commitment or marriage now.