Start by fitting the outlet (running outlet in the middle of a gutter run, stop end outlet at the end of a run) directly over the drain position - use a plumb line to check this (3).
Using 25mm x 5mm (1in x No. 10) screws, fix the outlet to the fascia, allowing for the fact that the far end of the gutter must be higher than the outlet by 10mm for every 6m of gutter (a fall of 1:600).
Now fit the end fascia bracket furthest away from the outlet, allowing for the required 1:600 fall. Check that the fascia board itself is level (it should be) and then use this as a reference line to position the bracket. Repeat with the other end fascia bracket if the outlet is in the middle of the gutter.
Tie a string line tightly from the end fascia bracket(s) to the outlet and use this as a guide for installing the remaining fascia brackets, which should be placed no more than 1m apart, working outwards from the outlet. Screw each bracket to the fascia with two or three gutter screws (4).