The hardest part is getting the fish to breed. After spawning, the trick is to get a few eggs away from the parents. Twenty eggs from any given spawn would be ideal, but even 1 egg is great if that's all you can get, particularly for the larger mouthbrooders. For substrate brooders, the eggs are attached to the substrate by invisible sticky threads. Scrape the eggs off with a fine, dull implement such as a butter knife.
Fish eggs are kind of rubbery and they survive being scraped off just fine.
Avoid using a sharp knife or a razor blade because that may slice into the actual egg. Incidentally, if the eggs are laid on a flowerpot or other removable object, you can take the pot right out of the water, scrape the eggs off the pot and put the pot with the rest of the eggs back in the aquarium. One technique that I have seen work well is to hold the fish in a net above the tank, with its mouth down. Then dribble a little water along the fish's side into its gills. The fish will often cough up the eggs into the net.