Negative keywords are those that you don't want your ad to appear when they are used in a search term. For example, if you are sending potential customers to a sales page for an iphone then you may decide that you don't want people who are looking for iphone reviews because they are in a research/data gathering frame of mind not buying mode. While they may become buyers when they gather enough information, you don't know how long that will take and you may not want to waste money on those sort of clicks. So you add 'review' and 'reviews' to your campaign negative keyword list. A good way to work out what your negative keywords should be is by doing a search on your main keywords and then seeing what keywords come up that aren't appropriate. You can then use the phrases that make them unsuitable in your negative keyword list. Hope that helps. Jill
A lot of this fine-tuning seems to be by trial and error, especially for newbies who don't want to, or cant, afford the services of experienced consultants. Still I'd have hoped that tools like Adcenter would have been more efficient.