Screws and screws with masonry anchors for heavy items are your best choice for hanging things on plaster walls without picture rail.
Hanging pictures on lath plaster wall.
For lighter items simply screwing into the plaster with a 1 1 4 drywall screw is usually enough to get the job done.
This system works by simply installing a rail along the wall and pictures then hang from cables attached to the rail and are fastened with hooks.
The best option mostly depends on the weight of the picture in question.
The ideal solution for hanging pictures on plaster is to use a picture hanging system like the all in one click rail cable hanging kit.
If the pictures are small and equipped with a wire on the back use a small picture hook and nail.