barking is difficult to stop but it can be done. First off, why is she barking? Does she want attention, is she bored, does she do it only when people come to the door, is she tied outside, or does she just do it all the time? All these things are important to know. For just general barking I'll tell you what I can. You'll need to teach her both the bark command and the quiet command. First you'll need to know of one thing that makes he bark (like the door bell). Say "bark" then do whatever makes he bark then say good dog! (no treats though). Then say "quiet" and stick a piece of yummy food (like sliced hot dog) in front of her nose so she starts sniffing and stops barking (they can't do both at the same time). As she is sniffing say she is sooooo goood, and then after a few seconds of that , give her the treat. Do this three times or so, and then make the treat less and less visible. Hold it further away and eventually behind your back. Make sure you always say bark before the thing that makes her bark and only give the treat if she stays quiet. Once she can be quiet on command with the treat behind your back for 3-5 seconds at a time for a few times you can then start making her do it longer and longer (not all in one session but over a few days or weeks) Once she will stop entirely for you without a visible treat (you still give him a treat even though you don't show it first) and he will bark on command, then he understands the commands. You will also want to work on using the commands at different distances from the dog (don't do this until he will do them without first seeing the treats and until he can hold the quiet for a long period) Give the commands at different distances and then in different positions (sitting in a chair,lying on the ground, behind the dog and what ever else you can think of.) Then once you can do this reliably you can start with real life situations (when a person actually comes to the door, when you are playing a game that riles him up).
If he does bark while you play with him, that is easy to solve, simply say "to bad" when he barks, get up take the toy and leave. He will learn when he barks during a game the game ends.
He also probably barks for attention which I'm sure you end up giving. By yelling "Shut up" at the dog, she thinks look I got her to pay attention to me, cool! Or you may poke her to startle her into stopping or just pay any attention whether positive or negative and she will continue. You must get up leave the room and leave her all by herself. If she stops get up and enter the room immediately giving her lots of love and also some treats, if she starts to bark, even once, then get up and leave again.
This will take time and mostly patience but if you really want her to stop then she needs training. I don't like the sort of stuff where you scare them into being quiet (spraying them or those collars with water of citronella) because firstly they can learn the difference between that collar and their normal collar and they will learn that the spry bottle thing only happens when your around so they will still bark when you are in a different room. And secondly because sometimes you want the dog to bark, like when an intruder is breaking in, your house is on fire, some strange people are in your yard in the middle of the night, there is a strange animal outside and other things. But by scaring them into never barking then they will do just that NEVER bark, because they are scared. Like lots of people punish their dog for growling. This is how a dog tells you stop what you're doing or I'm gonna bite. By punishing the growling behavior you are not somehow fixing the fact that whatever was making the dog uncomfortable now does not make him uncomfortable. It's just now when he is feeling threatened he will skip the growl and just bite the person, punishing the behavior solves nothing. Good Luck! and don't give up! If you need anymore training help, please ask.