How do you keep your nails from breaking?

I have been growing my nails for some time now and I am quite surprised they have grown to the length they are now as they hardly ever grew.  They are to me very strong, but I have realised that a few have gotten chips and I don't know why.  One of the longest, my right thumb, chipped today at the base and is now broken.  I tried to mend it but because I use it type on my black berry it's not the mend is not staying.  What can I do strengthen them?  What do you do?

I have seen some folks mend the nail using nail glue and the cloth of a teabag. It looked like it worked quite well. 

Here is a link to a youtube video on how to use the teabag to fix the nail! Hope this can help!!!!

Thanks much!  That's exactly what I tried.  But because I use the nail to type alot, it would not stay put....

Drink lots of water, take biotin (I would recommend checking with your doctor first), use a nail strengthener (my favorite is OPI Nail Envy), moisturize your cuticles, and never ever use your nails like "tools"

Try a base that has fiberglass fibers in it.

Since my pcp put me on Vitamin D supplements, my nails no longer break or split!!

Yup, vitamin D sure helps ! I also take supplements for my hair, and of course they also help my nails. They're stronger, maybe a bit thicker, and grow faster.

Check your nail ridges, if you can really see them and they're obvious, then it's an indication of not having enough iron, so iron supplements (if needed) help too.