greatSoiloutput = "greatSoils.shp"
where_clause1 = """
"DrainClass" = 'Well drained' OR "DrainClass" = 'Somewhat excessively drained'
"""
arcpy.Select_analysis(bigSoils, greatSoiloutput, where_clause1)
When formatted so it is easier to read.
So line 1... is the input shapefile, however, the path to the shapefile is not specified, so there has to be a reference to an environment variable (ie ... arcpy.env.workspace = r"c:\folder\subfolder")
line 2 and 4 ... contain triple double quotes to encase/enclose the code block shown (separated on its own line to facilitate reading). The actual code block uses the format for shapefiles, etc, Field names are enclosed in double quotes and text conditions on the right of the condition check are enclosed in single quotes.