Apparently if I girl's heartrate is increased, such as through fear or excitement, they can mix it up with an increased heartrate due to the person they're with, causing them to feel closer to them.
Also, hugging releases something from you that builds trust with the person hugging you.
And talking to a stranger about deep stuff, like really emotional and all that, for half an hour then staring into their eyes for four minutes has a very high chance of making you two fall in love.
So, for a first date:
Invite her to a scary movie or theme park.
Before you set off, tell her about the time your dog died and how you had a hard time in school, then ask her for her heartbreak stories. Then just stare into her eyes and say nothing. Once she gets creeped out, hopefully after the four minutes, just hug her. Make sure it's more than twenty seconds, that'll help. That'll help her trust you and therefore she won't think you're a serial killer, which removes the creepiness of staring into her eyes. Then go to said scary movie or theme park, make her poop herself with fear, and there you go.
A wife.