A numbers run is a geocaching trip focused on finding a very large number of geocaches, possibly 100 or more finds in a day.
A numbers run requires advance planning. Choose a cache-dense location that is near enough not to require a long drive to reach, yet far enough that you haven't found many caches there. Use a pocket query to identify a large number of traditional caches that can be found quickly. Focus on clusters of caches with lower difficulty ratings, located near convenient parking. Plan a route that minimizes driving time (e.g., avoiding left turns and known traffic problems), and plan more caches than you expect to find, so you can skip some (depending on what happens the day of the hunt) and still hit your target number.
Do not include multi-caches. If you're feeling ambitious, then you can solve some puzzle caches in advance and include them if they look like a quick find. Avoid caches with recent DNFs, or that require stealth. You may want to avoid known nano-caches, both because they can be hard to find and because signing and rerolling the log takes too long.
Include plans for bathroom breaks, food and beverages, fuel stops, etc. Decide in advance how you'll sign the logs, perhaps with a team name that is short, or with adhesive labels. Also decide how you'll keep track of which caches were found, which were skipped, etc., and how you're going to share the responsibility for driving.
Before the big day, get plenty of sleep, make sure you're hydrated, and generally take care of yourself. Make sure you have multiple GPS receivers with the selected caches, plenty of extra batteries, snacks, clipboards, etc. Basically, prepare for an all-day hunt.
The day of the numbers run, start early and just keep going. Once you start the hunt, everything is about efficiency. It isn't about individual finds; it's about the numbers run. If a cache is taking too long to find, then skip it and move on.