Running a restaurant is tough business. You have to deal with all personality types, and you have to adjust to having to deal constantly with people who all want something from you. From employees who want the perfect schedule to customers who want something for free to the restaurant owner who wants everything done their way, dealing with so many demands is an enormous task. Running a restaurant is going to be a balancing act. It doesn't take a miracle, but it does take fortitude.
Prioritize. Realize that you cannot be all things to all people. You can deal with things, though, in the order of importance. Make a list of the bare minimum daily tasks you need to perform to make sure the restaurant is open and serving people. Add and embellish it from there.
Listen to your employees. They will sometimes have been there for decades when you begin managing them. Hearing you tell them what to do after being there for a week or so is often hard to take. Empathize with that. While you must demand that they treat you with respect, you ultimately want to truly win the respect of your employees. A truly successful business has employees who care and people will not care if they are treated badly.
Take it in stride. Angry customers will try to manipulate you to get something for free. When some customers see a new manager, they see a chance to take advantage and get something for nothing. Stay true to the rules of the restaurant and don't give in simply because someone is yelling at you.
Take a time out if a customer gets abusive. If it is not the owner's policy to kick a customer out for speaking in an abusive way, realize it is your human right to avoid abuse. Tell him that you need a moment and walk away.
Get to know your customers if possible. Call a person by his name when possible.
Keep in clear communication with the owner. They key to survival in running a restaurant is happy medium of making a profit and making the owner happy. While these are often one and the same, sometimes they are not.