The schedule is what is going to make or break your experience in the QSR world. That's it. End of story. Period.
If you write a good schedule you'll be happy, productive, and profitable. If you write a bad schedule you'll be pissed off, unable to accomplish anything, and either out of business or changing careers. The weekly schedule is how you manage your primary set of tools—your subordinate team members. (On the flip side, the weekly schedule is THE central issue in their lives...but more on that later).
With enough exceptions to drive you to drink, rush periods can be predicted. Rush periods, by definition, are when large amounts of your business happen. Flipping burgers, this was lunch. Some days up to 75% of our business hit between 11am and 2pm. Slapping pizzas, I saw a lot of weeks when 50-65% of the weekly revenue happened in 5 hours every Friday. When you start talking large percentages of your daily or weekly business, you need to start thinking large percentages of your labor hours. If you short-staff your rush period you'll get nothing but pissed off customers, pissed off crew, and an alcohol problem for yourself.
Since you can't turn a profit if you work everyone all the time, pre and post rush hours need to be carefully considered. This is when the heavy lifting for your store happens. Before the rush, this is when your tomatoes get cut, your condiments get set out, utensils put in place, food stuffs readied for battle. After the rush, someone gets the trash and dishes out of the way, re-preps all the stuff you went thru before, keeps an eye on business to make sure late-lunchers don't go away feeling second rate. These periods will make or break your day, and you shouldn't give just anyone with a pulse these hours.
If you pay attention, you'll get a feel for when exactly your rush starts and stops on any given day. It's not written in stone. There are so many variables to when people eat, and sometimes the only way to win is with literally last-hour phone calls to keep people home or call them in. So while the labor matrix your district manager or operating partner or owner tells you to use is a very powerful tool...it is far from always right. That's why they pay you to write the schedule, and not a machine.
How do you write a solid schedule? Start by having everyone's current availability, in writing. Signed and dated. Nothing will destroy a good mood—or a good schedule—faster than someone coming up to you with a variation on, “But I told you every third Tuesday I have my back waxing appointment!” Be flexible, but when people tell you they can work a particular set of hours hold them to it. Knowing they've made a written commitment to be available for certain hours and days goes a long way towards keep people honest.
Stuff comes up. Doctors appointments, hot dates, family gatherings, once-in-a-lifetime rock concerts. The type of things we should be worried about, instead of work. Have a schedule request system in place for these situations—and use it. Giving someone a day off—especially if they're available five to seven days a week—will not ruin your business. It doesn't matter what the system is, exactly...but make sure it's written (so you and others can verify dates, track how many requests someone makes, etc), easy to get to for the crew, and something you can work into your schedule writing routine easily. I'm a big fan of a three ring binder, one page per schedule week. I worked for a guy who had a manilla envelope stapled to the wall next to the calendar in the office. Whatever works is what works.
Have a solid schedule routine. Start by scheduling to schedule, where you have a couple hours to just sit in the office or the dining room and write the schedule. This lets you focus on the task, do the labor calculations, make adjustments as needed. Resist the urge to “throw” a schedule together on the fly...you're not just putting numbers and names on paper, you're deciding the fate of your restaurant's next week.
Think “schedule” all week long. At least, have it in the back of your mind. If Susan is bucking for hours, coming in to help when there's call offs, make a note to reward that with more hours on the next schedule. If Billy has decided the post-rush trash run is more about his cigarette than the trash, make a note to yank those hours. The schedule is a great tool for motivating people...but only if you use it!
The needs of the business come first. Being flexible is admirable, and very necessary to keeping a happy workplace. At the same time, an employee who expects a full time schedule but can't work rush hours is not doing you any favors. A delivery driver who only wants to work Monday and Tuesday night? That's fine...except that driver had better understand he's only going to work 6 hours a week at most. Someone who wants to flip burgers only between 2 and 6pm? That's just taking post rush hours away from someone willing to come in at 10am and stay all day.
But at the same time, without employees who is going to take care of the customers? Remember everyone on your schedule has bills to pay, some more than others. It's not reasonable to use an adult with children to feed for a handful of hours if you can possibly help it. And while they have bills to pay, they have lives to lead too. You'd be pretty pissed off if you had to close, then come in and open. Or if you had a class to attend and your boss scheduled you to work at the same time. A little empathy, looking hard at finding solutions that meet everyone's needs instead of taking the easy route, will save you a lot of trouble in the long run with turnover.