Read it ALL. Don’t just see “Call out post for X” and think “that’s that, time to block them/spread this.” When you can, read each part (or send it to someone who can for you)
If there aren’t sources, ask for them
If they can’t provide sources 1) ask why (is it a valid reason, such as they don’t have the energy, or is it that they just don’t want to?) and 2) try and find them yourself on the person’s blog. No sources/evidence? Don’t reblog.
Read each source carefully and fully
Be critical- do you agree that this is evidence for what the call out post is saying about the person?
Try and find and understand the context of each source
If you can, look at all the notes (if it’s a post). Often people will post an original post, and miss out a possibly completely reasonable explanation that the person gave for the post later on
Look at OP, is there a bias in their reason for making the post? This doesn’t mean the post shouldn’t be taken seriously, but it indicates that the call out post may be spurred by personal reasons, and you should be even more critical of it and the evidence provided
Similarly, some points may be evidence for one “side” but not another. For example, for one person someone saying that aces are LGBT is evidence, for another someone saying aces aren’t LGBT is evidence
Look at the person who the call out is about. For example, are they a minor? If so, perhaps avoid spreading the post
Again; be critical, and assess each part. Don’t be scared to ask for OP’s logic, don’t be scared to ask for evidence, and don’t be scared to disagree. Call out posts are designed to open a dialog and bring awareness about a person.