Blender distinguishes between two different states of selection by the color of the outline:
yellow - active
orange - selected
black - unselected
open the select menu with the button
select an object by left clicking
add an additional object to selection by shift left clicking
Short cuts:
A Select all
alt-A Select none
ctl-I Invert current selection
B Select by drawing a box across desired objects
C Select by drawing a circle
In edit mode:
use buttons to right of mode select drop down to choose selecting vertices, edges, or surfaces.