Yeast health and fermentation temp control are tops for Tripel. Use some slurry from a recent batch of blond or make a starter. Lots of O2, yeast nutrient... you know the drill.
I think the Unibroue strain is still available from Wyeast. Its a badass yeast. If you don't have a strain you use often and are comfortable with, try it!
Good ol' table sugar is perfect for a Tripel. If you must substitute (I can't help myself, either), try honey or palm sugar (jaggery), both of which have more flavor than the light candi syrups (IMO).