Search engine marketing (SEM), attracting visitors to your site through pay-per-click keyword programs such as Google AdWords, requires a fair amount of initial testing and experimentation and then follow-through monitoring. Bruce Rhodes, circulation director at Harvard Business Review, uses SEM to help drive subscriber and prospect files. At the Circulation Management Conference last month, he shared some lessons he's learned along the way.

Brand Terms
The best performing keywords are usually your brand names and terms, but pay attention to who else is legitimately bidding and who is just driving up the price.

Remove Personal Biases
Figure out what is motivating a person to type in your brand or keywords. And just because you don't click on pay-per-click ads, doesn't mean your potential subscribers won't, said Rhodes.

Keep Monitoring
Someone needs to constantly monitor SEM activities, said Rhodes. Remember that it's an auction, and the bid management process can get incredibly complex if you let it. Always test.

Special Campaigns Are Difficult
Thematic, event-specific and seasonal campaigns are difficult to pull off. Success depends on integration of other campaign elements. Get ahead of the curve. Seasonal initiatives usually face a great deal of "noise" in the search channel.

Know Your Search Engines
Pop-ups from paid search are okay with Yahoo, forbidden with Google. Trademark protection;trademark owners can track trademarked terms within AdWords;is available with Google via a trademark complaint procedure but not with Yahoo.