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As summary, cause slight text wall, parsed through my own experience of the world.
Don't see a girl you like, and befriend her before trying to 'seduce' (or whatever word we're using) her. It's misleading and somewhat demeaning to befriend someone purely because you want a relationship.
Do make friends with girls. It is entirely possible for that to develop into something more. Go to clubs and interest groups, increase your chances, but try not to break the previous point.
Of course, feel free to replace girl with guy or whatever. I'm a guy, and I wouldn't be too happy if a close friend suddenly revealed they'd just wanted to hook up all along (not that that would likely happen with me being me).
Of course, I won't deny it is possible for the negative course to work out, and I'm not prepared to argue the morals of it.
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Smee, whilst I may be misinterpreting you, you appear to be making rather sweeping generalisations. As someone who could be considered a 'nice guy' without ulterior motives, it somewhat frustrates me to have people I like as friends spontaneously erupt at me because apparently men can't be nice to women without wanting sex. Course, I may well be misreading, and if so, feel free to ignore this - it isn't contributing to the topic.