There's no real trick in this case. Your main aim is to practice sparingly which will enable you to built up the skills to identify different tones in each text. Despite saying that, there are some things to look out for. When the writer or speaker doesn't go excessive or aggressive with their choice of words, you would sondier them to be conservative or controlled. When they do get angro or tend to attack, you would state that they're employing a scathing or harsh tone. When you see them saying heartfelt things, that's when they're being sympethetic or poignant. When they're appealing a lot to either fear or hip pocket nerve or whatever, that's when you suggest that they're adopting a sceptical or pleading tone. Lots of humour=sarcastic or amused. Lack the power to interest the audience=boring. There are lots of ways to approach tone-it's how you go about identifying them.