If you aren't good at reading other people's signals, then the following heuristic is a pretty good one: If you like A, and you are wondering whether A likes you, the answer is no.

This heuristic is terrible if you're trying to find a romantic partner since following it consistently will always lead you to believe that the people you're interested in and whose reciprocal interest isn't clear to you are not interested in you. If you live in a society where your potential partner isn't supposed to make overt signals about their romantic interests (because of gender roles or something), this may result in never finding a partner.

Also, suggesting that people who "aren't good at reading other people's signals" should condition anything based on the presence of uncertainty about reciprocal interest seems like it'll produce inconsistent results at best. In this case, I think they should take the potential failure mode and increase signaling until A (or a trusted friend) gives a unambiguous signal.