For fry, I used to siphon them out, and even use a scoop. Eventually I switched to just using a fine mesh net and have been doing that now for years.
For juveniles and adults I don't use a net, just my hands.
Believe me though, you've a lot to learn before getting to the fry collection stage. Check out the old threads over the last 4 or 5 years and see what you can gleen from those posts, and, do more research using your favorite search engine.