The plot is the sequence of events that take place in your story. Remember, you need to be selective of what events you include! You need to decide what's important for your readers. If you're writing a story about a school trip to the zoo, should you really include brushing your teeth in the morning? It might be important! Your character might spend the time contemplating the trip and looking at their own appearance. However, if you're just including it to fill up the word count or to start your story, ditch it!
Plots can't be overly complicated either! You should be able to sum up your plot in 3-4 bullet points. Remember, you only get 45 minutes in the exam for your story: 10 minutes to plan, 5 minutes to proofread, and 30 minutes to actually write your story. This doesn't leave a lot of time to spend on a long complex story with lots of plot twists! Keep your plot simple, but tell your story using imagination and all the techniques that you have learned.
Another point to consider is tension! Tension is how 'on edge' and 'restless' your audience is feeling. Tension usually builds up to a spike where your story reaches its climax. This should be mirrored in the language that you use. If the tension is low, use relaxing language and description to set the scene. When the tension increases, start using some short dramatic sentences as well as powerful verbs.