Now I know you learned about how to write about simple people like Bob in kindergarten, But .... we are totally over that. I doubt there is any seventh grade teacher in the world that will accept a story of Bob going to get a dog while it is suppose to be imaginative essay that he assigned. If you can't write any kind of story with more than 8 sentences, you need help. Hopefully this site will help you:

Bob went to the park. Bob saw Susie. Bob went to the swings wiht Susie. Bob had fun. Bob went too high on the swings. He fell off the swing and hurt his knee. Susie took Bob home.

Now, First write a rough draft of a story. Let's take the one above. You just brainstormed and wrote your ideas down. Now it's time to make it better. It depends on your abilities and your personality to make this short story exciting. Lets say you recently got a goldfish and are having problems with your friends. You might want to put your feelings in your writing. Look at the possible outcome:

Bob sighed. He looked gloomily at his goldfish. It just bubbled at him. Bob never knew his fish could be so boring. Any pet you get two days ago doesn't get boring that fast. Bob sighed again and grabbed his coat and walked out the door. Bob strolled down to the park. He had a fight with his best friend, Susie today. When he got to the park, he saw Susie there. She looked mad and somehow sad. Bob went over and said he was sorry. Susie apologized too and they went to play on the swings. Bob and Susie laughed as they went back and forth. It soon got competitive and they went higher and higher. Bob slipped of his swing and fell and hurt his knee. Susie took Bob home.

http://www.co.gaston.nc.us/FitnessandNutrition/images/ClipArt/swingset.gif

Now lets say you want to add a little more to your story. Instead of your feelings, add a your yourself to your character. What I mean is that you can add your life stories and lessons that really stands out in your mind. Let's say you got sprite spilled over your back at your lunch hour and your really depressed about it. Add it to your character and  you might feel better:

Bob had a really depressing day. First off, it turned out that his goldfish was completely uninteresting. He stared at it for hours trying to teach it tricks. Nothing, it just bubbled blankly infront of him. He only got it two days ago and now it turns out it is just a fish! Bob also got sprite sprayed all over him that morning while he was trying to get to class. Bob was very depressed.
Bob put down his homework and sighed. He needed to get out. He told his mom he was going for a walk. She nodded and continued with the cooking. Bob grabbed his jacket and walked out the door. As he walked down the cool, windy street, Bob remembered the fight he had last week with his best friend, Susie. She wanted him to go to her softball game but he forgot about it and went to Scott's party instead. She probably was still really mad. When he reached the park, he saw Susie sitting on a bench. She looked cold, lonely, and sad. Bob sighed again and walked over to her. He said he was awfully sorry that he missed her game and was glad they won. Susie smiled and forgave him. They both bought two ice cream cones and went down to the playground. Bob and susie finished their ice cream and went on the swings. They swung high and laughed hard when they laid back and swooped down again. Soon it became competitive and they both tried to see who can go the highest on the swings. When Bob tried to go back really hard, he slipped and fell off the swing. There was a thud as he hit the ground. Susie got off her swing and helped him up. Bob's knee was killing him, they both think he damaged it good some how. Susie helped Bob limp home. This was definitely a bad day for Bob.

Let me say that you can make as many changes to your stories as many times as you want. When you feel your writing piece is done, find an editor to help you with some improvements. Then you've got a Bob masterpiece!