I open a file from another user and the width of all the entities in the drawing are very wide, how can I set this width to be smaller.

The width occurs when the line weights button is depressed at the bottom of your screen.  To set the global visual width quickly, the objects need to have their line weights set to by layer.  Once the objects are by layer, for the line weight, go to the layer dialogue box and set the line weights, for all layers, to Default.  The final step is to open the Options dialogue box to the User Preferences tab and pick the Line weight Settings button.  Set the units listing to Inches and the default line weight pull-down to .010" as a starting width.  Plot a test page to see if this line weight is too heavy or light and change the default value up or down as needed.