How can I avoid running out of arrows?

I've been playing as Ranger and love my bow. But I'm having a very hard time because I'm always running out of arrows. I went through the first level of my quest to visit the leader, but can't progress further due to level - I only got 60 or so arrows on that level, another question's answer mentioned "hundreds".

When I was playing, whenever I ran out of arrows, I'd switch to melee, and this isn't always a good idea with strong-melee monsters. Because I was stubborn, I never picked up any other projectiles, and reading now, I realize I could have been keeping darts, daggers, or crossbow bolts.

nethack