i would like to know how to set out for cutting out window blocks and corner blocks? (plastering)?

Answer 1

Do you mean glass block? Glass block is not meant to be cut. You need to figure your design using full blocks. They make them in a variety of sizes. First get your layout then make your rough opening accordingly.

Answer 2

Assuming that you work with cinder blocks,put the whole block on the corner for each layer.
For the window,mark the edge of the window and put the finished edge of the block toward the opening and then fill the layer of blocks in either direction.Bear in mind the setting of the lower layer,cinder blocks should have joint in the center of the lower layer.