Recently I started a small campaign to get practice for my bigger campaign, with my friends. I introduced them too an essential NPC but I guess they thought the shipwrecked sailor was kinda boring.

I tried having the sailor use "Sailor Slang" and other stuff but it did not cut it for my players. I feel if my NPC creation is flawed. I am now worried that my NPCs might be not good in my bigger campaign.

So: How do you give NPCs personality?