Here's how to make hair prims which seem the most realistic.
The texture structure of your hair is very important, but the most important is the location of prims.

To build your first hair lock, rez a torus on the ground

Place this texture on the prim after youn have loaded it in Second Life

Edit your object, then click on the Texture tab, choose a texture, mark Apply immediately
Check the rotation (degrees) is set to 0.00

Change the end of Path cut of your prim F = 0.650

Change the size of your prim:
X = 0.276
Y = 0.500
Z = 0.577

Again change the Taper:
X = -1.00
Y = -1.00

Use a model of head sculpty to place your first hair locks.

When your hair is completed, remember to link your hair locks.