I don't wear perfume/cologne at all--I enjoy many scents, but there are so many people who are sensitive to fragrances that it seems rude (my SO can't stand perfumes, so I don't wear any anymore). I'd avoid it in crowds and offices, and recommend only wearing it if you're going to be spending time with someone that you already know enjoys it--otherwise there's absolutely nothing wrong with simply keeping clean. Most people smell pretty okay naturally unless they've gotten very sweaty/dirty or haven't washed in a long while. (Some people even prefer natural smells over perfumes.)
As for use: less than you think. Only you and someone in your "personal space" should be able to smell it. Don't spray it all over--use very small amounts on "pulse points": wrists, behind ears, throat. (This is harder to do with sprays than oils; it's easy to spray too much.) What kind: something you like. What smells good sprayed in the air in a department store may not smell as good along with your own natural scent, so you may want to test at home before wearing something in public. Ask someone at a department store or perfume shop to help you if you really have no idea what to get, and don't be embarrassed about it; if they are at all good at their job, they will be able to guide you toward scents of different types based on what you like--fruity, musky, floral, woodsy, light, heavy, what-have-you. If you don't know where to begin, think about other smells you like: fresh-cut grass, vanilla, ocean air, Irish Spring soap? If you have a significant other, ask what they like too...
(This is knowledge I have not used in a long enough time that I'd completely forgotten I had it!)
I am beginning to suspect that it is surprisingly common for intelligent, competent adults to somehow make it through the world for a few decades while missing some ordinary skill, like mailing a physical letter, folding a fitted sheet, depositing a check, or reading a bus schedule. Since these tasks are often presented atomically - or, worse, embedded implicitly into other instructions - and it is often possible to get around the need for them, this ignorance is not self-correcting. One can Google "how to deposit a check" and similar phrases, but the sorts of instructions that crop up are often misleading, rely on entangled and potentially similarly-deficient knowledge to be understandable, or are not so much instructions as they are tips and tricks and warnings for people who already know the basic procedure. Asking other people is more effective because they can respond to requests for clarification (and physically pointing at stuff is useful too), but embarrassing, since lacking these skills as an adult is stigmatized. (They are rarely even considered skills by people who have had them for a while.)
This seems like a bad situation. And - if I am correct and gaps like these are common - then it is something of a collective action problem to handle gap-filling without undue social drama. Supposedly, we're good at collective action problems, us rationalists, right? So I propose a thread for the purpose here, with the stipulation that all replies to gap announcements are to be constructive attempts at conveying the relevant procedural knowledge. No asking "how did you manage to be X years old without knowing that?" - if the gap-haver wishes to volunteer the information, that is fine, but asking is to be considered poor form.
(And yes, I have one. It's this: how in the world do people go about the supposedly atomic action of investing in the stock market? Here I am, sitting at my computer, and suppose I want a share of Apple - there isn't a button that says "Buy Our Stock" on their website. There goes my one idea. Where do I go and what do I do there?)