Someone asked the other day if I had tips on writing. I only have what I have learned from others. Here's the summary.
First, just write. Don't over think it. People who want to write but don't write often don't write because they are too busy thinking about writing. Maybe you have an idea you need to write about, maybe you don't. Either way, if you want to or need to write, just do it. Get something down. Get a draft, work from there.
So you now have a draft. It is most likely a mess. Decide if you need to write a second draft now that you have your ideas more firmly in place. If you think you do, do it quickly. If you don't, don't. Don't get hung up on the way things sound yet.
Ok, now you have your ideas down. Now correct glaring grammar errors. Not all of them, just the really horrible mistakes that are making your thoughts less coherent.
Next, edit out things. First, figure out if there are redundancies in the document. Not restatements, redundancies. Take them out. Then figure if you can make certain ideas more concise. Figure out how to use words more efficiently. Using fewer words to say something is always better as long as it doesn't sacrifice understanding. Finally, see if you have any parts you are hanging on to just because you like them. Be brutally honest about whether you need them. If not, take them out, no matter how much you love how they sound.
Now check your spelling.
Now do the in-depth grammar check, but remember this: Grammar ultimately is a secondary component of writing. More important than grammar is clarity. Your reader must be able to understand what you are saying (that isn't always accomplished by using more words, by the way.) If fixing some technical grammar error makes the sentence difficult or unintelligible, change it back. Grammar is supposed to serve understanding, that's why it exists.
Also, some things we were taught were bad grammar are either accepted now or really have always been accepted. The dangling preposition is a good example of this.
At this point, if you have time, put the document down and walk away. For at least an hour or so, a day or so if you can do that without getting lazy. Then read it again and see if you still like how it sounds and is clear. Remove things and edit as needed.
Now give it to someone to proofread. Remember that a proofreader is there to tell you if they can understand what you are saying in the document or to catch errors you missed, not to tell you whether or not they like it.
I know this sounds like a lot of work. Don't let anyone fool you: Writing is work. It can be fun and rewarding, but it is work. You can get better at it and make the process pretty quick once you get the hang of it, but writing well is something that takes effort.
Most of the time it's worth it.