Make the equation into slope-intercept form (y = mx + b)
8x+3y+24=0
8x+3y = -24
3y = -8x - 24
y = -8/3x - 8 (This is our answer)
Go to the orgin of the graph (0,0), down 8 units (this is call y-intercept; (0,8)). From (0,8) move down 8 units, then to the left 3 units. This is your slope; -8/3x.
The graph should look like a line from top left to bottom right.