wondered who Thing was 
my son is 5. i suppose the main thing i do is challenge stereotypes - re that's for girls/boys etc. i also intervened at school when i kept hearing he wasn't 'allowed' to play with girls anymore because boy X says so and it became apparent that boy X was having way too much sway over the boys in the class.
i spoke to the teacher the first time with little result and then i spoke to the teacher with ds and let him explain it in then 4yo terms of what was going on. then things did change and ds is happily playing with a range of children again rather than being dominated by this one boy. i gently made clear that the whole boys v girls, boys shouldn't play with girls or they're a wuss (sp?) etc culture was not inevitable and that school can and should challenge it as apart from anything else it is oppressive for those who don't fit into a fixed 'this is what boys/girls, do-play-think-feel' etc model (re: pretty much everyone if they aren't subjected to this oppressive policing).
i talk about feelings with him and i encourage the use of words to express emotional states like anger.
i exploit learning opportunities - e.g. watching mulan and talking about how brave she is and what a good soldier etc and how silly it is that she has to pretend to be a boy or she wouldn't be allowed to do anything because people think girls can't.... or boys can't.... etc etc.
i try to expose him to stories, films etc with positive and admirable heroines - the labyrinth is good.
i make a point of not going along with stupid treatment of him re: when he hurts himself it's perfectly ok to be upset and show you're hurt ffs.
i put together my own furniture and lift heavy objects and move things around etc solo and he sees how strong i am so he has a positive example that women are strong and capable and not weak and puny and have to get a man to do everything for them. when he does something that shows physical strength he says, 'look i'm strong like my mummy' 
likewise i let him see me assert myself, enforce my boundaries, challenge sexist behaviour/comments.
i'm not in a relationship but if i was i'd want to model equality and not conforming to gender roles in the home. that is a key one for people raising children in two parent families imo - you can say all you like but if they're seeing you picking up everyone's shit and scurrying around working whilst your partner sits on his arse then clearly they learn from that and actions speak louder than words for forming expectations about reality.