I have been told that my writing had the right idea and aim, but my words weren't strong enough to support that. I need some tips and tricks to help strengthen my writing. I've been told that I have been "telling and not showing". What does that mean? I need to know how to add more support into my words.
Create an image
Make it visual. Strive for vivid images.
Be careful with 'thought' words
You might want to avoid words like thinks, knows, believes, wants, realizes.
Be as specific as possible. Avoid redundancy, wordy phrases, and unnecessary modifiers.
Well, this closely relates to the answer I gave to your other question (history first?). Readers love things happening. They love people interacting with other people. They love emotions. They don't want to read how many centimetres your protagonist is tall, but that his opponent has to look up to him, stumbling backwards, his eyes wide open in fear. Don't tell your readers the measurement, but show them the effects it has on the characters and the events.
Chuck Palahniuk, author of Fight Club, gives the best possible how-to here: http://litreactor.com/essays/chuck-palahniuk/nuts-and-bolts-%E2%80%9Cthought%E2%80%9D-verbs