I thought I'll chip in with my two cents about seducing romancing an INTJ, which should apply to most INTJs regardless of gender.
Step 1: Study your INTJ carefully; your INTJ will have several interests. Pick a few and learn about them, enough that you can converse about them casually. True expertise is not required at all, as your INTJ will enjoy elucidating you, and you can capitalize on that weakness of ours to make us enjoy your company.
Step 2: Your INTJ may hold a set of social and moral values. I cannot stress how important it is to learn of these as soon as possible. When your values come into conflict with values we hold dear, we will immediately decide that you are not compatible with us. Other people may try to turn a blind eye, but not us. It doesn't even matter what we feel about you, we don't do feelings. Well, at least not yet.
Step 3: Take some time to learn about the most common flaws in logic and how to identify them. Nothing impresses and attracts an INTJ like being able to correctly identify flaws in logic. More interestingly, as INTJs, we often take shortcuts in logic when attempting to sway an audience, being poor communicators of internal logic and more interested in the result than the process of debate per se. Making your INTJ expand his/her arguments will definitely earn you some respect. And once you've earned our respect, you're already half-way there.
Step 4: You have now rendered yourself acceptable, being able to fit into your INTJ's long-term plans of how the world should work. With a little effort, you can make it so that to him or her, long-term planning must include you to be acceptable. At this point, your INTJ will be in love with you, but it may take some time before he/she realizes it.
Step 5: Flirting is something we cannot easily identify. Many people have become frustrated when flirting with INTJs, but this is easily overcome. Instead of flirting with us, just tell us as clinically and casually as possible, that you find yourself attracted and would like to try dating. Don't tell us that you would like to "take things to another level", we might think that what you mean is that we should proceed from becoming 'good friends' to 'best friends', or from 'best friends' to 'bestest friends'. Or from...well, you get the idea.
Step 6: An INTJ's basic form of communication is the logical argument. Engage them in it, expounding on the argument yourself if you agree with it, or attempt counter-argumentation if you disagree. Remember though, that the strength of your conviction does not correspond with the strength of your argument.
Step 7: INTJs are generally not physical people, and must be acclimated to touching. Start small, with hello or goodbye hugs and expand from there. An INTJ will, but rarely initiate physical contact. If you're a physical person, it may take quite awhile before getting your INTJ to act accordingly.
Again, I must stress that this isn't a fool-proof plan of getting INTJs, but it should work well. Good luck in getting that elusive INTJ!