Know what a blood feather looks like? When feathers are developing, they have a blood vessel that runs through the shaft. Break the forming feather, and it's a little blood straw, like those Tropicana OJ commercials, but with birds.
Don't clip those.
Also, if your bird has all its primaries, then the feathers that are there will help protect the ones that are coming in. Since you can't clip a blood feather (without unpleasantness) they grow in long, stick out, and get bumped as your girls run and flap around.
So give that a little thought, and try to put off clipping until after they're done feathering in.
Also, with other birds, being clipped to young can make them clumsy. I don't know if that's the case with hens.
You can do something called a "vanity clip" that takes most of the primaries back to the length of the secondaries, except the last two or three at the wing tip. That gives a little extra protection to any blood feathers, leaves a bird with a profile that *looks* like all the feathers are there, and can make it a little bit harder to get altitude.
If the choice is between a bit more risk of breaking a blood feather or getting eaten by the neighbor's dog, then I'd get out the scissors.