When you need to drill holes in plaster or cinder block in order to install wall anchors/plugs don’t start with the exact drill bit size that the anchor calls for. Instead, first start with a bit two sizes smaller than required and then enlarge the hole with next larger size bit (you may at this point be able to tap the anchor into place without having to further enlarge the hole). The reason for this is simple: as the material you are drilling into tends to crumble you can end up with the hole that is larger than the anchor diameter. If you start with a smaller diameter bit and do it in stages you can usually avoid this mishap.
If the worse happens and you end up with a hole too big to give a snug fit to the anchor all is not lost. It can be fixed with polyurethane glue (Gorilla Glue is one popular brand). Apply a little water to the hole and the exterior of the anchor and then squirt a small amount of glue into the hole. Coat the anchor with a little glue and insert into the hole. Leave this for an hour or two.The beauty of polyurethane glue is that it swells as it cures, thus providing a nice tight fit for the anchor. You should then be able to drive in the screw without the anchor slipping as you tighten. Although this procedure is a little time consuming it can save you from having to resort to more complicated fixes.