Unfortunately, prepositions are a problem in any language, and often you just need to memorize lots of examples until they seem natural. But: "in" usually means "inside," but it can be something physical: "I put the apple IN the box." We also tend to use it for intangible things like emotions or concepts: "I am IN love with him." "I said that IN English." "on" usually means "directly above:" "The apple is ON the table." It is also used for multi-person vehicles "I got ON a train/plane/bus/boat." Single-person vehicles usually use "in": "I got IN the car, I got IN the taxi." Horses and bicycles use "on", carts can use either. "On" is also used in specific idioms: "on track" (things are going according to plan), "on time" (not late or early), "on demand" (whenever something is requested), "on drugs" (addicted). Most of these you'd just have to memorize, there's not a lot of pattern. "At," as Aidan points out below is more regular: it means to be located specifically in location or time, and also means to be directed toward a given location, time, or direction. "I was home at 8:00" "I was at the movies" (Or both: "I was at the restaurant at 5:00"). Examples of direction: "I threw the ball AT him." "I stared AT the bird." "The squirrel made funny noises AT me." Your "and family to laugh at me" example is one of the latter.

At can be used for times and places but also for direction, such as “stop looking at me” or “they were laughing at me.” On can be confusing for things like transportation but a person usually gets on a bus, train but catches a cab and takes an Uber. In is used to refer to putting an object in.