I'm a dad of three younger girls (10, 7, and 2). The 10-year old has tons of friends over all the time from her school and dance class. They compete to see who can do the best on their math/STEM homework.
I'm also an employer at a technology company where we didn't have any women full-time until employee 20 or so (save a temp or two). Now we have 8 women, three in technical positions. They fit in great.
Anyway, the best thing I've found is to just give them the same opportunities and to challenge them. For example, we throw math and science trivia games up on the Apple TV and play as a family or with friends. They have fun and it's helped a ton with their math skills.
Also, I volunteer as a Lego Mindstorms coach. My girls don't participate yet but about half the team of 8 are girls. They all love it. A couple were shy at first but it helps that the other coach is a woman. We've had one or two girls that were really shy and didn't want to participate in the formal Lego matches. I casually talked to their parents one-on-one about how we could help those individual girls and we decided to just have them come "watch." Within like 10 minutes those girls joined right in and did great at the matches. I'd say they're some of the smartest on our team.
Same thing with the ladies at work. Two of them have become leaders and two of the others are working their way there.
It's been a matter of finding their talents and letting them go down that path exploring tech and supporting them by giving them CBT Nuggets or Plural Sight subscriptions. They go home at night an learn, explore, and practice.
The only thing I've really noticed is that if a woman tries to "put her foot down" they can be seen as brash (or worse) especially by male engineers. Where if a man does it he's seen as a leader.
I'm not sure how to handle that yet, but a smile goes a super long way.