How many targeted sites linked to you?
Of the specific prospects that you targeted in your campaigns, how many of them decided to link to you? You can manually verify this as well as using a tool such as Majestic.
How many non-targeted sites linked to you?
One of the side effects of a well-managed link building campaign is that the buzz generated will lead to other sites linking to you who you have not directly targeted. However, such links are as a direct result of your link building activity and therefore you should document them.
If you have to report to others on the total number of links you achieved through your link building activities, make sure you count these links from non-targeted sites in your reports. Once again, Majestic would be the go-to for this sort of information.
Overall site traffic?
Your link building campaigns will lead to an overall increase in the number of people visiting your website and you will be able to measure this using a standard analytics package such as Google Analytics.
Referrer traffic coming to your website
Have the new links that you generated led to an increase in the number of people who have reached your site by clicking on a link from an external site?
What goals have you achieved?
Has the increased traffic that your link building campaigns generated led to an increase in sales or progress in achieving another goal, for example sign-ups for your newsletter?
Search engine rankings for your important keywords
Over time, you’ll see an increase in the search engine rankings for your important keywords. Have you managed to influence the anchor text that external sites use to link to your website?
Which of your campaigns have been most successful?
Some of your campaigns will outperform others and it is impossible to tell beforehand which these will be. By monitoring carefully you will discover what works and what does not and therefore learn how to improve your success in the future.
How have your overall links grown over time?
General trends over time give a nice insight into how you are progressing. You can see cumulative and non-cumulative histories of your link acquisition over time in the Link Builder tool.