Gotcha, I thought your were asking something like that.
No exact answers here and you don't need any.
Yes, the pull should start more or less at the level of your face and you pull more or less to your face
. So in other words your HANDS are more or less at face level when you start the pull. but if it's a bit higher than that don't worry about it. It is not going to matter a lot if they end up being a bit higher or lower and you are not looking for some perfectly level plane. Just allow a natural line of pull toward you face. It is perfectly ok to vary it and pull more toward the neck or chin or forehead, etc. So look at mid-face like "neutral" and then you can play around with it and vary it between different sets or even in the same set.
Here's a pic of a good one. Looks like Mike Robertson doing one.
http://www.t-nation.com/img/photos/290rope-pull-mid.jpg
There's a beginning pic of that somewhere I've seen but I forget where. If I see it I'll tell you. But in that pic the hands start out at around face level as discussed and end up as shown in the pic link I posted. But you can tell that the actual pulley is well above his head and it's going to need to be, I would think in order to offset the weight.
You'll see people with their elbows a bit lower and that's not too bad. Make sure the elbows stay out as well and you don't want to make it into an external rotation with really heavy weights unless you know you are good and ready for that.
It's best to use a rope attachment. I'd say for most people if the handles when they are hanging are somewhere (more or less) at shoulder height that will work best. Then you just lean back enouth and adjust you feet closer or further until the angle is doable and gets your hands around face level as described. Everything else will even out in the wash.
Comes a point where the weight becomes very difficult to counterbalance, especially for light weights like me. Best to stick with high reps. But another option when it gets too heavy is to put a bench, if you can, perpendicularly between yourself and the pulley machine. Then, provided the bench is stable enought, you can put one foot up on the closest edge of the bench while also leaning back. That way you can apply a little offsetting force to the bench to supplement your bodyweight leaning against the weight. I hope I described that in a way that makes sense.
I think that about covers it. If you are or get to the point where you think the external rotators can handle it you can also do a face pull with an external rotation. Otherwise try to keep your elbows and hands level with each other througout. So it's much different than regular rows where the elbows are at the sides. In this case you want the elbows up in the air.The elbows following the hands, I think, is actually more important than where exactly you pull to.