Touch is a universal language, and the very first one for humans. If a loved one is going through a tough time, offer your touch and give this person a big hug. It may sound simple but for someone who is distressed, afraid or upset, warm touch can be soothing and even calm cardiovascular stress. As a result of a lowered stress response, research shows that hugging your friend can reduce her susceptibility to sickness.  Ask first to be sure hugging is an appropriate way to comfort your friend; some people do not like such physical gestures. Hold your friend close and rub her back. If she cries, let her cry into you. If you notice that your loved one seems to be trying hard to hold back what she is feeling, tell her it’s okay to show emotion. Many people feel guilty about expressing negative emotions. Others fear that they will be judged for not “keeping it together”. Tell your friend that you want her to feel whatever she’s feeling, and that you won’t judge her for it.  Say something like "It looks like you are having a hard time right now, and I want you to know that I'm here to listen if you want to vent" or "If you need to cry, you go right ahead". Psychologists insist that experiencing negative emotions is just as important as feeling positive states. Negative feelings teach us so much about the natural ups and downs of life. Therefore, expressing negative feelings, as opposed to suppressing them, can be instrumental to overall mental health. Your friend may want to lounge around all day watching reality TV or thumbing through gossip magazines. Your friend may want to talk about what’s bothering her, or she may want to talk about everything but that. She may want to go shopping, or simply take a nap. Plot out a few hours of distraction-free time to focus entirely on your hurting friend. Don’t come with a specific agenda; just be present. Your friend may not feel up to doing anything or may feel overwhelmed about making any decisions. But, it's smart to have a few ideas ready in case she wants to do...

TL;DR in Chinese:
如果可以，给对方一个拥抱。 鼓励对方表达情绪。 让对方知道只要他或她来找你，你都会留出时间给他们。 你可以带些你知道对方会喜欢的东西。 帮对方做事。