The final script

Here is how the script should look in the end:

# Chapter2Model1Modified.py 
# Import arcpy module 
import arcpy 
import csv 

arcpy.env.overwriteOutput = True

# Local variables: 
Bus_Stops = r"C:\Projects\SanFrancisco.gdb\SanFrancisco\Bus_Stops" 
CensusBlocks2010 = 
 r"C:\Projects\SanFrancisco.gdb\SanFrancisco\CensusBlocks2010" 
Inbound71 = r"C:\Projects\SanFrancisco.gdb\Chapter2Results\Inbound71" 
Inbound71_400ft_buffer = 
 r"C:\Projects\SanFrancisco.gdb\Chapter2Results\Inbound71_400ft_buffer"
Intersect71Census = 
 r"C:\Projects\SanFrancisco.gdb\Chapter2Results\Intersect71Census" 
 
# Process: Select 
arcpy.Select_analysis(Bus_Stops,  
                      Inbound71,  
                      "NAME = '71 IB' AND BUS_SIGNAG = 'Ferry Plaza'")
 
# Process: Buffer 
arcpy.Buffer_analysis(Inbound71,  
       ...