best way to prevent breakage

Lots of things can help!  No styling, especially with heat, will help a lot.  Putting it in a bun will certainly help by preventing tangles, providing you are holding the bun up with accessories that don't tear hear (no peeling bobby pins, accessories with sharp edges or sharp seams).  Braids are also good for the same reason (use thick elastics or ouchless ones -the ones with no metal piece to scratch your hair).

Other things that can help include making sure its not split, and getting a trim if it is (splits climb up the hair making the damage get worse, and making hair break off at the ends).  You don't usually need a ton of hair cut off, just the splits.

Also, make sure you aren't getting silicone buildup on your hair from conditioners.  This is usually ingredients in the conditioner that end in "cone" or "one", though not always.  This can make a coat on the hair which can break off and take pieces of your hair with it.  Its okay to use silicones, they do make hair less tangly, just be sure to clarify them off every once in awhile using a clarifying shampoo (any shampoo that says "clarifying" on it).  Don't use a clarifying shampoo all the time - once every 2 weeks to once every 2 months is plenty enough to remove the buildup.   Its very drying so you'll want to condition well after using it (either with a special treatment, or using conditioner twice).

If you live somewhere that has very hard water, a dilute vinegar rinse done last after you rinse out your conditioner also does wonders.  (It won't do much if you live somewhere that has nice soft water.  How do you tell? If your bath soap suds easily, you probably have soft water.  If it doesn't suds much at all you probably have hard water).  Put a tablespoon of vinegar in a cup of water and pour this over your head after conditioning - do not rinse out, the smell will evaporate as your hair dries.  Your hair will be much softer, shinier and less tangly.