what i would normally do:
1) Make sure the servo are correct in place according to manual.
2) Reset the transmitter back to neutral, all trim, sub trim, trim rate..etc..
3) Make sure the steering rods are of equal lenght (you can adj. toe-out later)
4) Attach the Servo horn - dead upright as Manti said!
5) Manually move the steering ankerman to the center.
6) Adj the steering post arm in equal lenght taking measurement from the distance between the 2 points.
That's all i would do normally.