Be accurate - work slowly and align edge to edge before marking your creases.
Before sharpening your creases, force them to place with your finger tips. When you are happy with the location of the folded flap, force it, by using a bone folder or your finger nail.
Try to avoid changing the direction of a fold line, especially with the wings. Reversing a fold line weaken the paper along it, and the wings will change the dihedral angle too easily.
Always refer to the paper reference points and not the printed template. The print may be misaligned on the paper, while reference points are absolute. By reference points we mean the edges and corners of the paper, and every new fold line that is based on them.
The symmetry of the wings has an utmost importance. This is the reason for having only one Wing Folding Line in the diagrams. Fold the marked wing first, and align the second to it, to have that perfect symmetry.