Despite sharing one of two total words, "day drinking" is actually nothing like "night drinking" (also referred to by some as “drinking”).
There are many unique considerations not encountered while Night Drinking. Let’s say you’re starting with brunch at 1pm, which means you’ll be pretending to enjoy your first gross mimosa (more like a mi-gross-a, amirite?!?! No, iamnotrite.) by 1:15pm. Now is the time to start thinking about the future. If you put yourself on the proper path to really getting to know a cheesesteak at 8pm or so, you’re looking good. But getting there the right way is critical.
The most important area of focus during your Day Drinking is not, in fact, the drinking; that part’s fairly easy. It’s the eating. Proper eating will be your buoy through the day and ensure you remain the kind of person others aren’t ashamed to be seen in public with, amidst all sorts of boring sober people who will spend their afternoons shopping for infinity scarves at Coldwater Creek. Far more importantly, it will provide the foundation for a (reasonably) hangover-less next morning, allowing you to go to the gym/office/local water park all bright-tailed and bushy-eyed. The second is especially true if you are Sam Waterston.
With all this in mind, do not stay out Night Drinking until 3am. A reasonable number of beers after work or at dinner is totally fine; you can even throw in a shot or two if it’s early enough and George Thorogood is insisting you do so. Show enough restraint to avoid waking up underneath your futon with your chinos on, and you will be rewarded.
Generally speaking, there are two kinds of brunch: 1) bottomless-booze brunches that will serve you 2 hours' worth of mimosas that are mostly just generic orange juice from concentrate, and/or bottom-shelf Bloody Marys that might also be from concentrate, and 2) regular brunches, which are nothing more than meals at a restaurant willing to serve eggs later than normal. These typically include one free drink in the aforementioned offensive mimosa/Bloody category, or possibly zero free drinks at all.