When I am developing an Idea for writing I like to really develop the concept before my first draft is even written. Many say that for your first draft you should just write and what comes out will be your premise. I have tried this and found it produces a very shallow piece. Your writing should convey your ideas and concepts, not create them.
Instead try the list approach. This is applicable for Stories, Theme pieces, Blog posts, Correspondence, Articles, etc. It even works for writing a speech you will give (this one is more complicated though because you have to convey your message verbally after writing it).
First plot out, in no specific order, the idea(s) you want to convey and then the key points to support them. This is when you should write as it comes; in the list phase. Then take them and organize your writing into an easier order to absorb. Once you have done this go to the next and most important step: Stars and Crosses.
When you have developed your list, add either Stars or Crosses to some of your points. Stars are put next to the points thats have the most value. These are to be address the most. Crosses means that you cross out (canceling out) the points you have written that can be omitted. These one are those with the least value. Adding them would seem meaningless to the reader and it would appear you are dragging on.
Also in putting your list together try to develop some concepts that are very interesting and/or humorous. These will be the points that will ice break your ideas. It is a key concept in making the reader interested. Your key points will keep them interested after that if you use Stars and Crosses effectively.
Now that you have done all this you are ready to write your draft. Take your lists and turn them into sentence and paragraph structure.
After you are done with your draft then it is time to revise, revise, revise. Be sure to check for spelling, grammar, etc. Mistakes in your english structure (or whatever language) will be very distracting to the reader.
Once you think you are done, read it out loud. Then revise again.
[...] Time between time. Unfortunately school scheduling is not perfect so I often end up with an hour or two between classes. This is waisted time unless I can find a way to use it. An advantage for me is that a good portion of my work can be done on the computer. If that is not the case for you, I would recommend bringing a notebook along to plot ideas and take notes. [...]