Some further tips on the tag-question subject-finding technique:

-Give them practice adding tags to sentences that require various 
pronouns in the tag --it, he, she, we, you, etc.
-If they are not fluent with the idea "pronoun", provide a list for 
them to choose from when creating tags.
-Do start with one-word subjects at the beginning of the sentence, but 
move quickly to subjects of more than one word.
-Use some sentences which have two noun phrases that agree with the tag 
pronoun, to demo that only the subject corresponds:

Mr. Rodriguez fired Mr. Jones, didn't he?
The Queen disapproves of Camilla Parker-Bowles, doesn't she?

-Rather than asking them what the pronoun in the tag "means" ("They" in 
  John's example), ask them which part of the base sentence the pronoun 
refers to.

-BEST TIP: ask them to use the tag pronoun as an "eraser" to rub out 
the appropriate part of the base sentence. Do this physically on the 
board or transparencies, whatever. This is a very effective demo for 
showing that subjects are often quite long.

-Be sure to move on eventually to sentences that have material before 
the subject, otherwise students will use a "first thing in the 
sentence" strategy. Ex.:

In the middle of the hot summer, our air conditioning system broke down.
Into the room rushed a monk with a long knife.

Such sentences sound odd with tags, because they wouldn't normally take 
one. You can try handling them as is, or you can demo for students how 
to "restore" the sentence to prototypical order:

Our air conditioning system broke down in the middle of the hot summer.
In the corner stood an ancient grandfather clock.

Be sure to work with passive sentences, so that students get past the 
"subject = doer of action" notion:

The town was devastated by the earthquake.
The old library has been torn down.
My uncle was injured in Iraq.

(Note that most passives in natural language do not have "by" phrases.)

Lastly, have students work on finding subjects in their own writing. 
You may help with this by choosing several sample essays and working 
with them on transparency, finding simpler sentences to work on first. 
Student writing is likely to have a number of difficult sentence types, 
however, such as sentences with subordinate clauses (which have as many 
subjects and predicates as they have clauses, and can be difficult to 
add tages to) and cleft sentences like "It was my Mom who finally 
solved the problem", which will (correctly) render "it" as subject, 
against the intuitive "my Mom" as subject.

You also have to be on the lookout for "existential there" sentences:

In the box were five cuddly puppies.
In the box were five cuddly puppies, weren't there?

When students come up with such examples, I just tell them that that' s 
a more complicated case that has to be handled at a higher level of 
grammar instruction, and move on to a different example.

It would be great if you would let us know how this technique works, if 
you try it.

Johanna Rubba, Assoc. Prof., Linguistics
Linguistics Minor Advisor
English Department
Cal Poly State University
San Luis Obispo, CA 93047
Tel. 805.756.2184
Dept. Tel. 805.756.6374
Home page:
http://www.cla.calpoly.edu/~jrubba

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