Knowing about humanism isn't necessarily the same as understanding humanism in particular, it doesn't tell you what is necessary for being a humanist. So what does it mean to be a humanist is there a club to join? Is there a church that you attend? What does being a humanist require?
All of the generalizations that are made about humanists should help point to one interesting fact about them: humanists are a very diverse group of people. Humanists may agree about many things, but they also disagree about many things. Humanists can be found on different sides of significant debates like capital punishment, abortion, euthanasia, taxation, etc.
Granted, you are much more likely to find humanists defending certain positions rather than others, but there is no requirement that they adopt particular conclusions on these or other issues. What is more important for humanism than the conclusions a person reaches are the principles they use when addressing difficult matters.
Humanists agree on principles of freethought, naturalism, empiricism, etc. Of course, even here we can find diversity. The more generally the principles are formulated, the more agreement there is even to the point where there is no dissent. When these principles are stated more specifically, however, the chances increase that individuals might not entirely agree with the specifics of that formulation. A person might feel that it is goes too far, doesn't go far enough, is worded incorrectly, etc.
Does this suggest that humanism doesn't really mean anything? I don't believe so. It's important to understand that humanism is not a dogma. Neither is it a doctrine, a creed, or a set of rules that a person must sign off on in oder to become a "member" of a club. Requiring people to agree to a specific set of statements in order for them to qualify as humanists or even as secular humanists would create a dogma and thus undermine the nature of humanism itself.
No, humanism is a set of principles, perspectives, and ideas about the world. Humanists are allowed to disagree not only on the conclusions they draw from those principles, but even on the formulation and extent of those principles themselves. Just because a person doesn't happen to subscribe 100% to every phrase and statement that appears in humanist documents doesn't mean that they cannot be humanists or even secular humanists. If this were necessary, then that would make humanism meaningless and there wouldn't be any real humanists.
What this means is that there isn't really anything to do in order to "be" a humanist. If you read any statements of humanist principles and find yourself agreeing with pretty much all of it and even when it comes to those points you don't entirely agree with you are inclined to accept the general thrust or direction of point being made, you are a humanist. Perhaps you are even a secular humanist, depending upon the way in which you approach and defend those principles.
This may sound like "conversion by definition," by which a person is "converted" to a point of view by simply redefining that point of view. It is not unreasonable to raise this objection because such things do happen, but that isn't the case here. Humanism is a name given to a set of principles and ideas which developed over the long course of human history. Humanism essentially existed before it had a name and before anyone thought to try to bring it all together into a coherent philosophy.
As a consequence of these principles existing as a part of human culture even apart from organized humanist philosophy, there are many people who continue down to this day to subscribe to them without also giving them a name. This is, to them, simply the best way to go about things and to approach life and there is certainly nothing wrong with that. A philosophy doesn't have to have a name in order to be good and effective.
Nevertheless, it is time that people come to understand that this philosophy does have a name, it does have a history, and it does offer serious alternatives to the religious, supernaturalistic philosophies which tend to dominate culture even today. Hopefully, as people come to realize this, they may think about these humanist principles actively rather than passively. Only when people are willing to stand up openly for humanist ideals will it have a real chance at improving society.