Make custom reports that show only natural search traffic, using a couple of basic custom filters.

Your site may have a page that can be reached through more than one URL variation – with and without WT.mc_id for example. This can cause search engine spiders to record more than one URL for that page, and that’s a bad thing. You can prevent the marker parameters (such as WT.mc_id) from being recorded by spiders, by using canonical link-tags.

If you have a PPC (pay-per-click) search effort happening, you may be allowing the PPC engines to loosely match your paid-for terms with various terms typed in by human searchers.

To keep abreast of what’s being matched to what (and maybe identify inappropriate matches that can be avoided by adding negative search terms, or get ideas for cheaper exact-match terms), try this report.