I hope it’s okay I answer this public? And thank you for the compliment.
Maybe I have a small advantage of being married 16 years. Or I just like Jack Harkness, a lot. I would say the big thing is the small things.If you want to be in a relationship, you notice the small things. You know what they like in their tea or coffee. You laugh at their jokes. If you’ve been a relationship for a while you have your inside jokes and shared experiences. If you’re just meeting someone, take a tip from Jack Harkness, smile, meet their eyes and introduce yourself. It’s a fine line between being creepy and being warm, but it’s about paying attention to the other person, and making sure they know you’re the center of their attention.
It’s also about being patient. That’s how I tend to write/think of Mystrade. Greg is warm and friendly, Mycroft is standofish and aloof. But he melts the ice simply by being there and letting Mycroft know he is willing to take as much time as he needs. John and Sherlock can have a similar dynamic, depending on how you’re writing them.
Like I said, in a more long term relationship, it’s about getting to know the other person. You get to know their lines, what jokes go too far, what things from the past you shouldn’t bring up if you want to keep you head attached to your shoulders. Real relationships have ups and downs, fights and moments of love. It can be as simple as holding hands. It can be as complicated as watching the sunrise together.