With digital phones, there is quite a bit that you can do in advance to reduce your overtime costs. Make sure that every voice cable is properly terminated and labeled, so cross-connects can be done quickly.
Test every voice jack to make sure the correct pairs are terminated. Remember, you need pins 3 and 6 for your digital phones. If some idiot installed the jacks with only pins 4 and 5, it’s a lot of labor to fix them. While you’re at it, make sure the jacks are wired consistently – either 586A or 586B. If some are different, the phone won’t come up. Either document it or fix it.
Then there are the obvious items that are often overlooked: is there backboard space, is there power, has the PRI circuit been extended from the demarc? Make sure everything is in place for your installation to be plug and play.