There are several keys to neat hand stitching. The key is preparation and layout. This is what I do and it works so well that I often get questions about it.
After the leather is ready to stitch, lay it flat on a granite slab. Take a pair of wing dividers and lightly scribe a line down the edges of the strap roughly 1/8th inch from the edge. If you are creasing your leather, the scribe line should fall on the crease. Next layout where your holes are going to be. Personally I use pricking irons, either 7,8,9 or 10 SPI. Prick the stitch locations and follow up by piercing the leather with a polished diamond awl. Lightly coat the mating surfaces with Barge cement and allow it to tack dry. Slipping two needles through matching yet opposite holes and gently and evenly push the pieces together. Clamp the work into a stitching horse and begin stitching right to left away from you. After passing the right needle through the work, do not pull tight rather leave a small loop. Pass the left needle over top of the right thread and as the left needle exits the right side hole, pull on the loop of thread while pushing the needle. This make certain that the two threads are separate of each other, then pull both tight at the same time. Another key is consistant thread tension. After completeing the stitches and trimming the thread, pound the stitches with a flat faced hammer against that granite slab. If done correctly and after lots of practice, the stitches will be as even and tight and consistant as any made with a machine.
I'll attach a couple of photos that show some finished work.
Dave