This is how I do it. Just wondering if there is a better or different way. I like to mount the arm on the servo at the center of the travel arc of 60 degrees both directions. I start out by using the neutral point of the servo arm being parellel to the hinge line, say it's the aileron. Then by moving the arm 60 degrees one direction, I make a mark on the wing where the pushrod will connect. Move it the other direction and make a mark on the wing at the other spot. Now draw a line between the two dots and down to the hinge line. This is where I mount the control horn at center. Is this how you guys do it? I am trying to get the best mechanical advantage.

As you said, there are a bunch of ways to do it. Sometimes I just mount the servo and connect the push rod to the arm and horn, I always have my controls made up in advance, then find the spot where the horn mounts close to the hinge line and is a straight, linear throw so there is no binding. Sort of let the servo pick the spot. Sometimes I have just used a straight edge run from the servo arm across the control surface and marked it out. I can do it a lot of ways but I do try to get a hinge in the area of where the arm will be mounted. I do this off the plans during the build. With an ARF the arm will go wherever you can get a straight shot with the control rod.
Not sure if I said that so anyone could understand it but the key is NO BINDING.

You can find some good hints here:

http://www.airfieldmodels.com/inform...d_linkages.htm

What you are doing is correct:

1) Finding the range of the pushrod moved by the servo: This should be done for the outer position on the servo horn.

2) Dividing that range in two halves: This may not be correct for ailerons of cambered wings, which need a mechanical differential (more deflection up than down)

3) Locating the line of the holes of the control surface's horn right over the hinge's line and perpendicular to the control surface.

4) Verify that there is no bidding for the maximum deflection of the control surface for the inner position on the control surface's horn. (Sometimes the bidding is caused just by twisting of the pushrod in the full deflection position, specially when the two horns do not rotate in the same plane).

I just mount the horn so the holes for the clevis connection are direclty over the hinge line and on the movable surface so it's either in line with pushrod coming off the arm (aileron) or where no binding occurs (rudder, elevator) depending on the type of rods I'm using.

For trainers and other types with one piece elevators, it's works real nice tot have the pushrod come staright out the rear of the fuselage. Very clean and no hole in the rear side of the fuse for the elevator.