All good stuff here and worth noting, but don't get too frightened! Grass isn't scary, just a few different hazards.
To add to a point Backpacker made about lighting and marking, grass runways tend to "look different" on approach. They tend to be all different shapes and sizes, often with the runway not quite so clearly defined as a nice rectangular strip of tarmac. You get fewer cues to being on the right glide path, and when I was learning (and afterwards) I tended to find the first approach at a different grass strip could be a bit ragged. As always: never be too proud or too scared to go around, even from runway height if necessary.