Nope, theres no absolute way to tell its fertile before setting it that I'm aware of. You can crack them open and look for the bulls eye on the yolk to get an idea of fertility, but obviously you can't incubate those
How early you can tell if they'regrowing depends on your eggs. If they're white, tan or brown eggs, I can usually tell by day 3 or 4. If they're blue, green or dark brown, it takes longer. Some of my hens lay eggs so dark I can never tell if they're growing, so I sniff them occasionally to check for off smells and they go into lockdown and hatch...or not.
A good rule of thumb is to keep them until day 10 if you aren't sure about them