The real rule is "be interested". Being interesting follows from that, but being interested is the part you can control.
I've found that when people have persistent difficulties finding a partner, it's almost always because they aren't actually interested in the women they date, but have some platonic ideal of a woman that they think they ought to date and so are dating the wrong people.
Sure (I too have read 'How to Win Friends and Influence People') - but that only works if the other person is already interested in you. One sided interest just comes across as creepy.
Depends on the context. One-sided interest that's fixated on one particular characteristic comes across as creepy - it's obvious when it's a physical characteristic, but it's also just as creepy to be particularly interested in someone's career, or house, or car, or any other thing. One-sided interest that's diffuse tends to become two-sided interest, because it makes you seem engaged with the world, and that's a very attractive quality for a lot of people. Basically, be interested in everyone and you'll find that everyone is interested in you, while if you're interested in only one person she probably won't be interested in you.
I've found that when people have persistent difficulties finding a partner, it's almost always because they aren't actually interested in the women they date, but have some platonic ideal of a woman that they think they ought to date and so are dating the wrong people.