Let me give you a little different perspective than the others here. Their advice is valid, and is actually what I suggest you follow, but here is a little bit of a second opinion.
You craft the world by your perception of it. If you associate strongly with the spirits named in the Necronomicon, and you feel a connection to those works, there is no reason they shouldn't work for you. However, the magick must be your own. If you truly feel this strong a connection with the Necronomicon, you must find which entities within it work best for you for this particular act, you must discover them and speak with them on your own, you must decide which of them is right for the job, and you must find the proper method of calling them up.
Use what is written in the Necronomicon as a template, but make the rituals specific to you. For example, I don't always use a chart of magickal correspondences in my rituals, but rather choose stones and herbs and other correspondences based on my own experiences and intuition.
In the end, true magick is all about altering your perception of the universe. By calling on Shub-Niggurath to seduce this guy, what you are really doing is altering your own subconscious mind into believing that the spirits have claimed him for you, thereby causing you to "know," deep within yourself, that you should have no fear in walking up to him and asking him out. By altering your perception of reality, you are giving yourself the power to shape it. If the spell fails, you may try again, or it may be revealed unto you that this person has some traits that are not necessarily ones you would want in a partner and thus the spirits have protected you from making a mistake.
But please be careful, and remember that, should you really use magick to dominate his mind, you are acting on selfish desires that could hurt him and come back to bite you. No good relationship has ever started by force. In thirty years of practicing the art, and in a great many relationships, I never once used magick to seduce and subdue a partner, simply to help me find one.