See the DRAWORDER command.
By default entities are (re)drawn in the order in which were added to the DWG: new entities are added at the back of the file, hence they are drawn last. This means they are drawn on top of previously added entities.
A simple trick to bring entities on top without having to rely on DRAWORDER is to perform a cut/paste operation:
- Select the entity or entities.
- Press Ctrl X to cut the selection and copy it to the clipboard.
- Press Ctrl V; the selection is attached to the crosshairs.
- Press the Enter key to paste the entities at their original location.
The pasted entities become the latest or 'youngest' entities, and therefore sit on top off 'older' entities.