Once your link developers have had some time to settle in and learn the ropes, you'll want to start tracking their performance and seeing where they may need improvement, praise or, in extreme cases, termination. You should create a template that will allow your link developers to log their progress throughout the month, as well as a template for an end-of-month report in report card-style format.
There are several elements you should consider when evaluating a link developer's performance:
1. The number of links they actually build
2. The number of links they request (i.e. the number of requests they have sent out for the month)
3. The types of links they're obtaining (reciprocals vs. article submissions vs. pure one-way links)
4. The quality of the links they're obtaining (the linked page's pagerank, the number of links on the inbound links page, the anchor text being used, the value of the domain from which the link originates)
5. The retention of acquired links (you can measure the rate of growth of your backlinks as a whole from month to month; if you have more than one developer working on the same site, you might spot-check their links to get an idea of their individual retention rates)
Also, be sure to look at the most important thing of all: your movement in the search engine result pages of the three major engines (be sure to account for any ageing processes that may be in place). And remember that quantity does not always equal quality. Developer "A" may obtain 300 links per month, and your site may move from position 10 to position 8, but this may not be as productive as Developer "B", who obtains 100 links, moving your site from position 10 to position 6.