Google has been busy lately with all the improvements it's made to the Google AdWords user interface. One of the newest features, "Segments", can really help take your campaign performance to a new level.
This feature allows user to review campaign performance data in a multitude of ways. This can be done by the day of week (performance by day of the week, regardless of the date), year (performance by year), network (Google Search, Content, and Search Partners), device (computer or mobile), experiment (Campaign Experiment results), click type (click to call or URL clicks), and performance by either the day, week, month, quarter, or year.
To make using the segmented data simpler, start by focusing on one campaign in your account that's struggling. Check to see if there's one keyword that's still relevant but not converting to results. Consult Segments to see, time-wise, when the decline started. This may help you associate this date with a particular event that coincided with the decrease.
This tool can also help you tailor your advertising around the times and days when you get the most activity, proving to be a huge time and budget saver.
Of all the new gadgets Google has added to AdWords as of late, this new feature may prove to be the most underrated.