Welcome!
New hatchlings can be sexed by "popping", something done by breeders, usually. Once they get older, and are able to control their muscles more, that is not very effective.
Older snakes can be sexed by probing.
Sometimes, you can tell by their tails, but that is not always effective. Males will have thicker tails that don't taper as much after the vent, and female tails typically taper more after the vent.
Another way is with lighter babies, like Amels, Snows, etc, you can hold them up to a light, and see whether they have hemipenes or not.
And lastly (that I can think of) sometimes females will lay slugs (infertile) eggs. Then, you know you have a female. LOL