Another thing i always try to do when putting a brand new string on-
I bring the string up to tune about 1 to 2 steps below the final note it will be at... then i leave it for an hour or so before bringing it up to the final note. This is especially good if you are changing or putting on all strings at once.

When i adjust the tuning on a string, I do two safety things-
1. I always turn my head so my face is turned away as much as possible.
2. And I hover my other hand over the fret board near the middle while I turn the peg. That last part would definitely keep the string length from whipping up at full length to reach my face.  So, in rapid succession I pluck the string to hear it sound, then quickly hover that same hand closely over the middle of the fret board while turning the peg with left hand.
If you are tightening a string a long ways (as when just putting it on), you can even lay a little washcloth over the fretboard as you are getting the string 'in the ballpark'.

Richard, I am very paranoid when tuning a new instrument and I wear protective goggles when I do, but I have a lot of dulcimers with old strings and I am always worried that one will break while Im playing. Unfortunately goggles arent always an option, so I'm mostly trying to gauge what a worst case scenario would look like. 

Robin, I could definitely imagine that it hurts. I personally take a mechanical pencil and scribble some graphite into the slots before putting the strings on, and this helps a lot with friction at the nut. 

Jamie, that is good to hear, and I imagine that where it whips is somewhat erratic, so I hope that stays consistent for you. It's good to hear that nobody has an instance of being whipped in the face. 

Thanks all

Re strings breaking:in my experience they fly away from the musician's face when breaking while playing.Tuning up new strings I  always shut my eyes tight in that last little bit to get them up to pitch.

I've been whipped by a string before-- it smarts.  

I re-tune a lot and would, once in a great while, break a string.  What I noticed, finally, is my string breaks occurred when I was tuning a string down.  What was happening:  the string would stick at the nut, so, when tuning down, the string was "pushing" against where the string was stuck in the nut, causing the break.  Now, when I re-tune, I put downward pressure on the strings between the tuning pegs and the nut-- -- no breaks.  

I've never had one break while playing. Wear safety glasses as a precaution.

Hey folks. I use pretty heavy gauge strings on my dulcimers and don't change them very often. So far, I haven't had a string break while playing, but I've always been kind of paranoid, since my face is directly above the strings. My fear is that the string will snap, whip up, and hit me in the eye faster than I can blink. I'm just hoping for some anecdotes about strings breaking while playing: if anyone has ever been hurt by one and where the strings tend to go when they do break.
Thanks,
Nate