So your client's better-than-average homepage has slipped from fourth or fifth place on the first SERP to first or second place on the second page for a particular keyword, and they want you (or your copywriter) to tinker with the copy. Before making any changes to keyword density, image or title tags, or even the "About Us" section, Karon Thackston says you should ask your clients some questions first.
Are conversions suffering? If so, then perhaps a change in copy is necessary. But it could also be due to a new shopping cart or other usability changes that degraded the visitor experience. If conversions are good--leave the darn copy alone.
If products or services have changed, then of course the copy needs to reflect that. But if there hasn't been a downturn in site traffic, phone calls or overall business, Thackston says that tweaking the copy just for the sake of better rankings may be a mistake. She does post an addendum to the initial article, noting that testing new copy is also an option.