I think that we can help in two main areas:
1. The early and continual encouragement of women getting into STEM.
As the father of three girls I feel I have the opportunity to help provide encouragement to my daughters and their friends at a young age. It is important to actively encourage our daughters, nieces, etc. to pursue interests in STEM.
Immediately throw out any kids catalogs that blatantly show girls playing with dolls and boys with science kits.
Man up and be a male role model at home that does not reinforce gender biased housework.
Start teaching your daughters about science, math and computer programming.
Volunteer your time with groups like Girls Who Code, etc.
Address comments like, "I'm a girl, it's OK I am not smart with computers" immediately. Men should have no tolerance for comments like these.
2. Challenging the male-centric existing software engineering and technology culture
Have a zero tolerance policy for things like assuming that the women in the group is in marketing or design.
Have a zero tolerance policy for ANY sexist remarks.
Actively encourage any female engineers that you manage, are on your team, friends to give talks, sit on panels, voice their opinions, etc.
Contribute to being a part of a safe working environment.
Actively invite the women in your company to a safe forum to discuss this very issue. Don't get a bunch of guys together to try to figure this out.
Please also see my other Quora answer: What are some of the biggest mistakes men make when managing women?
Source: Quora