Hey Tammy, that’s really a question every writer has to answer for themselves. For me, the most important thing is consistency. I am better at writing long pieces if I do a little bit every day. Like, half an hour. If you have more time, you can do more, of course. But the important thing is to work continually. Aside from that, there are many blog posts and books on this topic. I suggest you start there.
Be professional. When you submit a résumé, don’t type it in ALL CAPS and please don’t avoid the caps lock like the plague. Know how to use it without looking incompetent. Write in complete sentences with proper grammar. Of course, there will be exceptions, but even with the exceptions, you must keep it professional. You’re building their view of you.