Ideas and Content
A good writer develops a plan before writing. The writer needs a main idea and a purpose. The main idea is the point the writer wants to make. The purpose is the reason for writing. For instance, the purpose of some  writing is to inform with facts. Other writing is meant to persuade, using convincing ideas,or simply to entertain with an interesting story.

When you prepare to write, first consider possible topics. Choose the one that interests you the most. Then decide whether you want to inform, persuade,or entertain your audience. Write possible main ideas, and let  your ideas flow as you plan. Don’t be afraid to change your mind. Select the main idea that makes the most sense as you consider who your audience is.
List details that fit your topic and support your main idea. Add interesting information that will appeal to your audience. Now decide which details are the strongest.Look at the following example, which shows the plans  of one writer who has listed details and then eliminated the weakest ones.

Main Idea: Persuade Mom to adopt a dog
Details:
Will teach me responsibility              Will keep me company
Will play with me                               Some dogs fluffy
Promise to walk it every day             Will take care of it
I saw cute dog in park

FOCUS
Check that the details you use support your main idea. Eliminate details that are off the subject or weak.