You know how you can use Dimensions to break out AdWords performance by period of time—by hour of day, day, day of week, etc.—for reporting or optimization? You might already be doing that, actually. (If not, check out Dimensions → Time.)
Imagine if you could see not just performance by day or hour, but performance by day and hour. Meaning, for example: On Mondays, from 9 to noon, the cost-per-lead (CPL) is $15, and from noon to 5, the CPL is $11. On Tuesdays, from 9 to 1, the CPL is $17, and from 1 to 5, the CPL is $14. And so on.
Imagine, particularly, the chance for optimization.
With the data you can now get with Dimensions, and not too much work in Excel, you can create mini, usable dimensions like that, and bid adjust for savings.
1. Export the regular day of week and hour of day performance Dimensions for the date range you want to go through. (I added calls from an external source, and calculated CPL myself. Unless you have a fair number of leads invisible to AdWords, this is an extra step.)
2. Create a day-hour expanded CPL grid, with the value of each intersecting cell equaling the product of the corresponding day and hour CPLs, e.g., the Monday at 8 cell equals Monday’s CPL multiplied by 8’s CPL. This shows the relative CPL of each day-hour block. If you want, you can use Conditional Formatting → Color Scales on the values. This makes it obvious which day-hour CPLs are above or below average—and looks pretty neat.This already provides some interesting information, namely they tend to get the best bang for during the later hours earlier in the week and the, well, less good value during the earlier hours later in the week.
3. Convert that into the adjustments needed to reduce the higher CPLs to the average expanded CPL. (I used the average as a “satisfactory” baseline, but you can really use any figure.) Just create a second grid with each intersecting cell equaling one minus the average expanded CPL divided by the day-hour expanded CPL. A positive percentage is a negative bid adjustment—lower by that percentage. (Conversely, or in addition, you can try using the negative percentages as positive bid adjustments, to gain lead volume, albeit with a possible higher CPL.)