Being quite experienced with this hero, my strategy is bascially the same everytime. Shoot for maxing expunge and totems, with extra points into heal and ult whenever possible. Crystal goes into elemental binding (usually don't bother with bounce attack unless I have large amounts of crystal laying around), then massive attack dmg build all the way. Usually aim for 3-5 points into attack. The rest into agility. Gear wise can vary slightly, but generally: attack orb, blink totem, agi gloves, grab dmg helmet or agi helmet instead of leather for armor/extra dmg. May buy dragon's on occasion or even sun talisman.
Note: although the blink totem is very helpful for extra dps, have found it to be a 0 upgrade wonder. The fulte I suppose would be great too for chasing down enemy heroes, if you got the cash. Again, in that regard, another 0 upgrade wonder...
Attached is a single game replay for anyone who's bored or interested, or both.
Just some pregame info:
1v8, lvl 54, 54 kills. Gear: +5 totem, +5 agi gloves, +5 attack orb, and +5 agi helm. I realize this is a little exaggerated

Have also heard mention of a hybrid tank version shammy. This of course would include putting points into heal and pain. I've even seen a couple of these on bnets. Seems to work well. Just another way to play him....
Your Strategies?