Have you longed to be a comedian about town, a nut, a fool, a secret font of wisdom, hilarious? That is, do you want to be funny? I advise against it. It's a long, hard, cold road. Fraught with perils, it can be dangerous and nerve wracking. But if you reject my first advice I won't abandon you. If you just have to make people laugh, if the comedian persona has clutched you in its ferocious paws, I say "Go for it!" Clearly you have no choice. But heed my advice below.
1. Set jokes will be your doom. My father used to ask all grocery store cashiers if they took Rubles. I heard that joke thousands of times. Was it new to each cashier? Mostly. Was it a bad joke? No, no, it's fine as a joke for our purposes. Did he perfect it through such intensive repetition? Perhaps. But still I must speak against it. You cannot keep running the same material without becoming complacent, unnatural. You've got to stay hungry, and you must always be testing new material or you won't notice it when people start humoring you all of the time instead of just some of the time.
2. Know your audience. Professional comedians complain about tough audiences, but I laugh at professional comedians! Their audience is made up of a specific sub group of people who at least theoretically like comedians and are even willing to pay to see them. Your audience is anyone! Anyone! Sure, some of them are up for a laugh, but some of them are easily insulted, some of them have almost no sense of humor, and some of them don't even know what to do when a joke happens and will stare at you, bewildered. You will need to instant read your audience. You will need to pitch jokes to their level (which you had to deduce only a second ago). You will need to adjust your level of daring to their level of daring (all jokes are daring, which means they can also, in the wrong context, end up as mean, offensive, disturbing, and/or inappropriate). And you may even need to guide them along in receiving your joke properly, perhaps with a twinkle or a chuckle that lets them know that, no, the director of your Library doesn't actually fly about in her own fleet of jets equipped with bowling alleys, you're just being wacky. Sometimes this is enough to let them know they can laugh, which may be all the stronger for the relief in it.
3. You cannot joke all the time. Joking thrives on its relation to the serious, to the real. Real life is like cream and comedy is like the air and whisking. If you whisk nothing you have nothing. But whisk the right amount of cream and you get whipped cream, which, of course, is hilarious. Keep whipping the whipped cream and you get butter, which is excellent on toast and is the famous secret of French cooking.
4. It's okay to challenge your audience. While it is imperative to know your audience (remember point two?) that doesn't mean you can't challenge their limits. Plus, you can only know your audience so much, and throwing out a wide net of material not only keeps them off balance and amuseable, but also helps you refine your material and become better able to actually read your audience in the first place. Writing here I have little or no opportunity to read you as my audience, and so my comedy approaches have been especially diverse. And so too it's a nice approach if in this sort of situation you can present a lot of challenging or minor material in a way that lets it fail without too much notice. For instance, an early joke in this piece was "...I laugh at professional comedians!" This was a joke far better than my usual standard, but also one that, if you missed it, you didn't stop and say "I didn't get that joke." You merely, possibly, didn't know there was a joke there in the first place. There is an added benefit here that once it's pointed out as a joke it's unmissable. As to the absurdist humor in point number three, what with the meaningless analogy to butter, it was even more challenging as far as comedy goes, and usually if I did that kind of joke in person I'd have to laugh winningly to assure people that I'm not a lunatic, I'm just being funny. But here, in text, since I can know that at the least you are the sort of person who would actually read all of this post, you might be up for a slightly bizarre and challenging burst of absurdist humor.
5. Try to be nice. This is a tough one because it cuts out at least 30 percent of your material off the top. Professionals perhaps can't afford this one, or, possibly, don't need the restriction due to the depersonalized and formalized relation of their work. You, however do need this, because even though it may seem like comedy comes first, it doesn't. Humanity comes first. Warm laughs are beautiful. Hard, brittle, exploding and snickering laughs are, well, great, I won't lie, but great like fast food; crappy if you actually are paying attention, obesity and cancer causing, and horrible to the world. So be careful. Besides, for all that professional comedians like to go on about the aggressiveness of comedy, its violence (i.e. I killed them out there) they're mostly wrong. You do not want to be a master jokester in order to express your hatred of the world and force people to laugh against their will. Really, you don't. You want to be funny because laughing is fun and sweet, soul purifying, unifying, wise, healthy, and full of love. You want to be funny because it it a force for good! So, remember that out there. And go knock 'em dead.