First step I do is compare to butterfly caterpillars (pics of eggs) known to use the plant as host. If it's a possible match, leave them alone for further observation. If not, investigate other critters that might lay eggs that look like that. Usually don't figure it out unless they obviously match a butterfly. Depending on the plant, I might remove the egg mass and isolate it in a container with a lid to see what comes out. Many beneficial predators lay eggs on plants, I'd hate to kill any of those.