Using a pair of ladies knee socks from the Dollar Tree I made these tights in about 30 min. 
The technique you use I think depends on the sock design for  mine I used both  socks.  
To determine how long they needed to be I  held the sock up to the doll and held the sock  in place as I wanted the knitted band for my bottom hem, and measured up the doll to allow for a the waist band... I allowed 1/2 to fold over and then cut for lengh  My cut was about 3 inches from the heel of the sock
Then I measure for the front seam from the dolls waist to her crotch ... on mine this was 3.5 inches.
I sewed a seam from the waist to the 3.5 inch mark  - done for both pieces front and back
I folded my waist band over .5 inch and stitched it 
Then join front to back  
matching crotch and legs/front to back stitch along entire inside leg seam 
No hem needed as I used the pink knit band on the sock as my hem ...
tights for ONE dollar !!
 Pixie Faire has great
 patterns and tutorials !!

 
