That goes double for the packed lunch. If you're going to pass up on the opportunity for a buffalo fried chicken sandwich or a ranch-dressing-soaked salad - wonders, all - you still deserve to revel in your own delights. You may have to excuse yourself when your co-workers head out to forage for their own victuals, but you still have every right to suggest to them that you, too, intend, as a talking goat once put it, to live deliciously.
This means, first, that you should ignore most of the advice that others dish out about plating your workplace dishes. Contrary to almost all received wisdom, you should feel free to heat up smelly food in the microwave. For one thing, the attempt to restrict culinary odors is, all too often, about policing the cultures and cuisines of nonwhite people. In any case, it's possible to be irritated by all sorts of food-related things, including the mere sound of chewing. As the Kitchn's Rachel Sugar puts it, "You hate the smell of curry, I hate the smell of tuna, and yet we must coexist together in functional harmony."
Instead of living in fear of office puritans, aim to delight them. By all means, perfume the floor with spices and citrus and oil. Your co-workers may act irritated, but really they're just going to be jealous. When they ask after the smells, take their query for what it really is: an opportunity to brag about what a terrific cook you are.
That said, you absolutely should not actually cook your food in the shared microwave - with some exceptions given for prepackaged meals designed to be prepared that way. The odiferousness of fish, for example, is entirely excusable, but nuking it in an environment that will turn it to rubber? That's just rude to the fish itself. Your meal, be it leftover spaghetti or mapo tofu, should be largely complete by the time you leave home in the morning.
(It should also probably go without saying, but do not, under any circumstances, try to roast chicken in the shared toaster oven. This is your office, not your sophomore-year dorm room. The toaster oven is for toast, and the fact that no one ever seems to actually eat toast at work is no excuse to confront your unwitting colleagues with the possibility of salmonella.)
You must also prepare your meal with an eye toward the possibility of theft. While some etiquette guides instruct you on what to do once the miscreant has made off with your food, you're better off discouraging them from taking it in the first place. Yes, labeling may help, but only if the thief seeks plausible deniability. You're better off storing your food in containers that no one wants to look at in the first place.
If you are bringing a sandwich, avoid the urge to wrap it delicately in butcher paper as they would at some artisanal hoagie shop: You will only make your colleagues want to unwrap it before you can. Elegant glass containers, likewise, may make your lunch look like a museum piece, which seems lovely, but is actually like taunting Danny Ocean when you own a poorly secured casino.
Better to cram your homemade delicacies in brown paper bags or used cottage cheese containers (washed, of course). Your lunch should be a showpiece while you are eating it, but it need not present itself beforehand. In any case, it's always best to keep things simple: Containers with separate compartments rarely separate the components properly. Bringing a host of smaller ones, meanwhile, will just make you look fussy. Besides, you'll always forget some crucial one, leaving yourself with quinoa, thinly sliced celery and nothing that actually makes you want to eat the two of them together.
However dingy your plasticware may be, though, there's no reason to leave it lying on your desk unwashed after you finish your meal. Given how much time you have, presumably, already saved by not trekking out to buy it, there is no reason that you shouldn't take a moment or two to clean your containers. If the desk lunch is fundamentally sad, then there is surely nothing sadder than shoveling it into your face at a messy desk. And lest you need more motivation, you'll never have to worry about whether you're responsible for those disquieting emails from HR about pests in the building.
But the most important thing to remember about bringing your lunch to work is that you will be eating it early. Maybe it's the effort that goes into readying it in the first place, but you'll surely end up stuffing your face before the clock rings noon. And that's fine, but it also demands that you follow one last etiquette guideline, not out of respect for your co-workers, but in kindness to your future self: Remember, always, to bring an extra snack. After all, you're sure to be hungry again by late afternoon.