You start at the hotel Seiser Alm (parking fee) from where you can take several trails (even one with a lift) which all converge at Saltnerhütte at the base of the Schlern ascent. There is not so much as a shortest or most beautiful hike - they all are pretty much the same. Saltnerhütte is posted at almost every trail crossing.
Altitude Gain: 800m
This is the easiest and far most popilar ascent towards the Schlern plateau. From Saltnerhütte the trail winds through the flank of the northern Schlern wall (stay on the trail - it's used thousands of times each year) until it meets the plateau. Here go to the "Schlernhäuser" refuge and onwards to Petz (25min from Schlernhäuser). You can go on to the second summit on Schlern, Burgstall (Monte Cavallo) which offers a nice view at the two towers Santnerspitze and Euringerspitze from above. The estimated aditional time is some 30 - 45 min one way.
Just normal hiking gear.