Here is a short list of things I do and some things I have heard suggested:

• Consume media created by members of disadvantaged groups
• Notice when members of disadvantaged groups are absent from a particular setting. Ask yourself or others why this might be the case, and whether this serves the desired objectives, or if there's even clarity on what the desired objectives are. (Example: holding a meeting on a college campus that lacks public parking.)
• If you attend professional conferences, ask organizers what they are doing to ensure all presentation proposals get fair consideration. (If you're so inclined, ask what they are doing to support diversity among presenters.)
• Update towards the belief that, regardless of your good intentions, members of disadvantaged groups may interpret certain things you say uncharitably. Avoid saying such things, or take pains to avoid offloading your discomfort onto them. For examples of things to watch out for, you may find it helpful to read Derailing for Dummies.

Some addenda:

• If you have experiences that you feel make you better able to empathize with members of a disadvantaged group, great! When you are with members of the disadvantaged group, do not bring up these experiences unless you are specifically asked.
• Do not claim to share an identity with members of the disadvantaged group unless explicitly and enthusiastically invited to do so. Even so, this dispensation is good only when you're among the people who extended it to you. (Example: a campus LGBTQA group whose members are persistently and vocally excited about the "and allies!" bit.)
• If you feel someone is stereotyping you unfairly, consider whether you are the target audience for this piece of media. Do not reply, with a possible exception being for when you are being named specifically (and not referred to by group identity.)
• Carefully consider the relative magnitude of a wrong you have suffered before airing righteous indignation, even as a group bonding activity.