I want to make a long (endless) pearl necklace without a clasp.
Can anybody share their secret on how to finish this necklace?

Usually I string pearls with double silk thread and overhand knots.

Sheila

Tie a knot in your silk, string 4 pearls without knots...leave about 4 - 6" and then tie another knot. String your remaining pearls as you normally would. Knot them. When you get to the end, thread the needle through the first pearl that you originally place on the silk. Tie your next knot, repeat with the rest of the 4 pearls. Then you will have the two ends to just tie off.
Good luck.