Selling in person is different from selling with the written word. About a month ago I read a post on the Future Now blog entitled 1,000 Tips for Selling Online Without Paying a Copywriter. The guts of this post is that you need to hire a good copywriter if you want to sell.
If you expect to market your products or services make sure the words you use sell. I know, you can write well, you know your product or service better then a hired gun but don't skimp on a persuasive direct response writer when it comes to your marketing materials.
Remember, you want your copy to grab the reader's attention and walk them to a point of conversion. A good copywriter knows what makes people take action. When people write their own sales literature they often try to communicate everything about a product since it matters to them; but usually forget about what matter to the reader and why the reader should take action. Have you seen sales copy without 'call to action' triggers? I know I have.
Do yourself a favor and find a great copywriter who understands direct response marketing and let them take a stab at some of your writing needs. If they are good you won't be disappointed.
If you need some recommendations let me know and I will share some of my resources.