I find railroading doesn't work for me ... I seem to untwist the strand of cotton if I do it. I use a trolley needle instead (it's a laying tool that attaches to my finger/thumb/.
Otherwise tension is a big thing that will throw your neatness out. I find a good tight hoop or frame and effort to keep the tightness of my stitches consistent help here. If you think your tension might be a bit whack an easy way to find out is to try stitching a small piece on canvas as opposed to material (the big holes show loose or tight stitches up really easily in my experience).
Otherwise to be honest your work doesn't look too bad (we are all our own worst critics).