Lots of busy students and professionals ask "How can I become a better writer?"  
Writing well is a high value skill that can help you in life and work.  Getting your ideas across in a clear and effective manner means that you are head-and-shoulders above other writers.  Many people struggle to write well, making writing a great way to differentiate yourself.
An easy way to become a better writer is to focus on the writing process.  Different instructors will use different terms, or slightly different steps, but they are largely talking about the same process. 
So, what it the writing process?  Here it is, in six steps.  
1) Answer the question
Answering the questions means you "begin the with the end in mind".  What do you want your readers to take away from your piece?  Once you have that figured out, you can work backward from it.  Defining your purpose is the most important step, especially for nonfiction.  
2) Brainstorm
Next, get all of your ideas out of your head and down on paper.  Don't edit or censor yourself, just go nuts.  If you are writing about movies and you can't stop thinking about mangoes, write it down and add the idea to the pile.  See where your mind goes next, after mangoes.  Maybe you will wind up somewhere interesting?  I prefer to use mind maps for brainstorming. 
3) Outline
Now that you've finished brainstorming, take all your ideas and start to organize them.  Put them in lists and under headings.  Now you can start to choose between ideas (but don't throw anything out yet).  Remember to keep the end purpose in mind.  
Outlining will accomplish a couple of things.  It will clarify your ideas and it will allow you to put together a plan.  It makes it so much easier to write when you have an outline to put together.  
4) Write
Now you can "put pen to paper" or put fingers to keyboard.  Take your outline and start fleshing out the ideas.  Don't worry too much about amazing sentence structure or word choice.  Just keep moving through your outline.  If you start feeling stuck, it may help to go back to step one, and remind yourself about what you are trying to communicate.  I try to move quickly and not think too much during the writing process, otherwise I get sidetracked.  
5) Edit
Stephen King famously wrote "kill your darlings".  Welcome to the killing room floor, the editing step.  Start cutting words, sentences, ideas, and anything else that detracts from the purpose you outlined in step number 1.  Once you are done with the slaughter, you can start rewriting what you've got left.   Pay attention to things like word choice, transitions, marker language, and punctuation.  You want your writing to flow and have a sense of direction.  (Unless you are an amazing writer, in which case, you are excused from the rest of this article!)
Some professional writers work with editors.  I've never worked with an editor, but I would assume its a professional courtesy for a writer to give at least one round of revisions before handing if off to an editor.
6) Publish
Get your work out in the world.  Let the people read it and get their feedback.  Incorporate it into your future work.  This step is easier than ever with the advent of the Internet.
As a writer and someone who has taught writing to young authors, I still struggle with this process. It is very tempting to skip steps and go straight to the writing step.  Don't do it.  You will be amazed at how working this process will improve your writing.