Suggestions for sightreading practice

I'd like to work on my sightreading skills. At present, I am playing one hymn (that I haven't played before) at each practice session as part of my warmups, selected at random from a hymnal. Any other suggestions for an approach to improving this skill?

Leaving apart many other considerations, you might start playing in a very slow motion pace pieces you can read easily and play well, capturing effortlessly at sight the two or three staves. You then may advance little-by-little.