by way of SearchEngineWatch.com

• Add keywords gradually, and in new ad groups when possible. Ideally, ad groups should consist of no more than 15-20 tightly-related keywords around a theme.
• Test one thing at a time. If you just added new keywords to an existing ad group, don’t start an ad copy test at the same time. If you just turned off the search network, don’t start fiddling with your bids too much.
• Test ad copy systematically. Always test against a control ad — don’t throw everything out and start anew.
• If you’ve made major changes to your landing page(s), don’t change your PPC campaign too. In fact, you should test the new landing page against the existing page and pick the winner of the test, instead of changing your pages first.
• Interpret test results from each PPC engine, and each channel (search vs. content) independently. They can and do act differently, and what works in one may flop in another. It’s OK to take one engine’s “winners” and try them in another engine, but don’t be surprised if they turn out to be “losers” in the new engine!

read the full article here:  SEW