Men, as much as I encourage you to become feminists or at least support feminism, I do not require it of you. You're allowed to choose not to be a feminist. You are, of course, allowed to join the movement if you want. However, whether you choose to join or not, there are some things you need to know:
1) Don't derail the discussion.
For example, if people are talking about Female Genital Mutilation, do NOT jump in and start ranting about male circumcision. While the two are similar in nature and have some parallels, they have a stark contrast in severity. If people are talking about barriers women face in the workforce, don't start going on about how there are some feminine jobs that men have a hard time entering. If people are talking about one thing, don't try to shift the topic to something pertaining to men's rights. While men's rights are of importance to feminism and do merit mention in some situations, by shifting a conversation to men's rights you are saying that men's rights should come first, and that whatever women's problem they're talking about couldn't possibly be anywhere near as important as men's problems.
And when you do bring up men's rights issues, don't be a jerk. Don't accuse people of being stupid and misandrist just because they're talking about a problem as it pertains to women, and you really shouldn't insult them and call them gendered slurs such as "bitch" or "cunt."
2) Don't make it about you.
You don't rape women? You don't say sexist things? You're not like that? That's nice, here's a cookie. Just because you don't do something doesn't mean it doesn't happen. Just because you don't think a certain way doesn't mean no one does. Just because you don't know any misogynist people doesn't mean they don't exist. Just because you live in a blissful equality bubble doesn't mean sexism doesn't exist. And when people talk about male privilege, don't write it off just because you don't consider yourself "a sexist." A lot of people have unexamined privilege that they ought to take a look at, and a lot of people have prejudices they may not be aware of. Even women tend to harbor internalized misogyny. So be open the fact that you may be a little bit sexist, and be open to the fact that sexism exists outside your little social bubble.
3) Don't try to take the reigns.
Maybe you have some great ideas as to how feminism can move forward as a social movement and adapt to the changing times. STOP. Especially if you're new or not even a part of the movement. You may make suggestions if you're educated about what feminism actually is and why it operates the way it does. However, outright saying that feminism should change its name, that feminists should adopt a different demeanor, that feminists should shift their focus and prioritize different things, and then getting angry and frustrated when people say "no, we're not gonna do that" is not okay. It may be about equality, but your place is not to lead the movement and make major decisions for all feminists. That's not how it works.
4) HEY! LISTEN!
Just because you have a mom and a sister and a girlfriend and some female friends does not mean you are an expert on women's issues or what it means to be a woman. In order to really understand it, LISTEN to women when they talk about what it's like to be a woman, and read books and blogs about feminism. Do not reject ideas just because you don't think they pertain to the women you know. Do not tell women to just suck it up and overcome whatever obstacles are in their path, don't tell them to just "get" some self-esteem or tell them to stop being so weak. You will show your privilege and you will sound ignorant as all hell.