How should a glider pilot signal turns to the towplane?
The glider flying handbook is wrong. The glider signals to the tow pilot by moving to the outside of the turn. 

We glider pilots have been trying toget the FAA to fix this and many other errors in the GFH for years. See the newsgroup rec.aviation.soaring

Also, many tow pilots ignore tow steering directions because they think they know better than the glider pilot where the lift is.