I stick my round nose pliers in the hole and give a hefty tug and see if they move.
The trick I have found to good crimping is about 4 or five steps. Lets see if I can explain it.
First I usually use two crimps on each end. That way they are double secure.
I use the crimp tool and put the dent in the bead making sure the wires are not crossed over.
This is where it gets different than most folks. I turn the crimp pliers sideways and and use the end of the crimp pliers to pinch the dent closed just a little bit more.
I take two flat nosed pliers and grab the crimp on each side of the bend and give it a bit more of a bend gently.
Then I use the round part of the pliers to fold the crimp in half. Make sure the handles of your crimp are behind the opening of the bend since as you fold you want the motion to match the bend.
Then I take my flat nose pliers and give the bent crimp a gentle squeeze to ensure it is closed well.
Be gentle with the crimps, under too much work or pressure they can break the beading wire and your necklace will still come apart.
I also know that cheap crimps just do not do the job professional crimps do. It is worth the pennies to ensure your necklace stays together.
Over the years I have been selling jewelry I only know of four necklaces that came apart and they were all worn for years before the strand broke above the crimp, no beads were lost.
Szarka