One of the best ways to ensure that your writing assignments will result in your clients loving your work is to find out who their target audience is. When you are new at freelance writing you might not always understand why you're writing an article. Knowing the purpose of the piece you are writing is going to help you ensure that you are writing it in a way that will get your client results that will make them want to hire you to write for them again.
If you simply get directions to write a 264 word article with a seven word title and 2% keyword density with no more than 3 paragraphs and a question at the end this can seem easily doable but if you don't know who's going to read it how will you know what to put in it? The end result will probably be fluff. Even search engine food can have multiple purposes and even a simple keyword article can be something that will bring success to your career as a writer.
When clients want an SEO article you should be writing with the intention of writing an intriguing article that will pique both the human readers as well as the search engine spider's interest so that the article will get clicks and indexed. When clients want a sales letter there's going to be a clear call to action as well as examples of why it's a great buy, ways of overcoming objections and a lot of answering questions that the reader might have. When you write copy for a website you are selling not only a product but a brand. When you write a press release you have to follow a specific formula. As you can see, not all writing assignments require the same approach.
Knowing where the projects you write will go and who the client wants to have read them will help you be a better writer. You need to know if you're writing for a "made for adsense" site versus a wiki site. You should have a clear idea of who you're writing for and what the desired result for the piece is before you get started on your first draft.
So, learn what the purpose of each writing gig is. I can almost promise that the client won't think it's a silly question when you ask. They'll see that you want to do your best to write for their targeted audience. The end result will be that you can better research and craft a piece of work that will hit the mark and get the client results as well as get you some repeat business and word of mouth referrals.