Of course grammar is important as is spelling, but nowadays with the spell checks and grammar checks, even the poorest of spellers can get a good article through. Copy writing is not about elegant prose and syntax, copy writing is a specific discipline.
Copy writing is all about feelings and psychology, about how people react and what they are in quest for and certainly does not need to involve big and complicated sentences, these will simply put the readers off. What a copy should be aiming at is reaching over to the reader using a psychological approach, that is the success behind a copy, after all selling and marketing is all about knowing how people will react to such and such a product or be attracted to it.
Copy writing is really as easy as it sounds, really anyone can become a copy writer as long as they keep the 'key' objective in mind: you must connect with the target. It is essential that the reader understands that he or she actually needs your service or product, that they will benefit from it. You must be able to portray the importance of the product or service your are providing or even virtually convince them that it is the very thing they need, they just hadn't realized before!
If you start writing without actually knowing your potential customers inside out then you will just be wasting your time. Getting to know your customers means knowing which way to influence their decisions. There are undoubtedly certain phrases or words that catch their attention, some expressions typical to the kind of products or service you are marketing, find those and you're half way there. What you need to do is research work. Believe it or not this is the essential and biggest part of your work in copy writing, and not the writing itself!
So basically a good copy writer has to be a psychologist of some sort! Think of those adverts on TV, some are so old you just can't believe their still on. Well that's because they still work! The marketing of those products is still going full swing, although the ad may seem obsolete, it works well on people.
This is why there are certain key words or phrases that will always stir people, during your research work, this is what you should be looking for: the magic words for your market!