Pay attention to what they’re really saying and doing. This is not a time for denial. “This can’t be happening” is a good way to get yourself beaten to a pulp, it’s the reaction they’re looking for. If you know the person, you probably understand the motive behind what they’re doing.
Don’t show fear or vulnerability. People are less likely to attack confident others, bullies go after people who are already fearful. If you tend toward fearfulness or insecurity, face that as its own problem and work on building your inner strength. Learn to set your fears or grief aside in a crisis and become calm – not angry, calm. This puts you in control of the situation. It will also help, if you try and build your strength. Remember that bullies look for victims, not opponents.
Answer anything they say politely without insults. This breaks the script of a typical fight. It also sets up a fear factor of its own. Remember the “little old Japanese guy” in any karate movie. He’s always very polite no matter how many insults including racist insults the bully is shouting – if you respond like that, without a raised voice or any insulting words, it sounds as if you have some hidden defence you know is unbeatable. Showing them that you have inner strength, will often put them off.
Try not to anger them to come at you. Put simply: do not provoke them. Do not start insulting them by group (stupid jokes, dumb whatever, racist comments, sexist comments, the list goes on.). If they are bullies, just looking for anyone who seems vulnerable, try to avoid their usual paths and hangouts. Stay out of their way.
If it’s a personal fight over something that has happened – they are jealous because someone they are attracted to, likes you more, or something you own that they wish they had, or if they feel betrayed, or if you did betray them in some way like gossip, then try conflict resolution. Remember that if a friend suddenly turns on you for no reason you can think of, the likeliest thing is that someone lied to them and the best way to solve it is to compare notes about who told you what. You would not believe how many pointless fights start because someone else was jealous of a friendship or just malicious.
Make sure you know what they want to do with you. Don’t escalate it by getting back at them. Don’t ever escalate a conflict with someone in a long term situation like school, work, family, or roommate. That’s a road to blowing up your life and costs far more than the moment’s satisfaction of revenge.
Do not attack first. Only fight back if they attack first; try to avoid getting to that point. If you fight back after they attack, then you can claim self defense. Remember that for it to be considered self-defense, you need to only do enough fighting for them to be unable to harm you. It is not legal to harm someone any further, after they are already away from your danger zone.
Take physical threats seriously. Use minimal force, and escape the situation. Use all authorities and resources available to deal with the situation if you’re physically threatened – police, school authorities, workplace authorities, help lines, you name it. You should be able to live without the fear of being physically attacked. If you are living with people who hit you, move out. If you’re underage and it’s family, there are resources, use help lines.