Depending on the type of plant you're working with, you'll begin with cutting or dividing your plant.
For succulents, you typically begin with leaf cutting, a process where you remove a handful of leaves from the stem, place them on a flat surface (like a cookie sheet covered in soil), wait for them to scab over before planting in the soil to grow tiny "pups."
For monsteras and philodendrons, I use a trimming technique where I cut off an offshoot that already has one or two root notches (the little bumps where roots are beginning to grow again).
Depending on how many stems your plant has, you can also use root division, where you essentially split the existing plant into smaller bunches of plants. (Pro-tip: Try this technique if you already plan to repot, since it can be a little messy.)
For fiddle leaf figs, you can trim individual leaves close to the main stem.
There are a few other techniques that are privy to specific plant varieties, but these are a pretty good place to start.