respond appropriately with no to short phrases  

Bag

Set of objects which the child understands the names of

1. Take the objects out of the bag one at a time, for each item say to the child "It's a [name of object]" for example "It's an apple". Look to the child for confirmation that it's an apple (as if you are not quite sure). Then, with certainty, say "Yes, it's an apple";

2. After a few items, start to get the occasional item wrong (use exactly the same not-quite-sure facial expression you used before). E.g. "It's a pencil" (but it's a toy car). Can the child tell you that it isn't? If not, have a look at the item again and pretend to suddenly realise you were wrong, say "(oh) No, it's not a pencil. It's a car.

3. Repeat.

Two toy animals or dolls (each with a name)

(Optional) things that the dolls can use, e.g. tea set

1. Jemima always gets things right, Polly finds it more difficult. Tell Jemima (or whatever you name your toy) to do a few things, for example walk, run, jump. Make her do the actions correctly. The child can also have a go at telling her to do the actions.

2. Polly (or whatever you call the other toy) has a go. Tell Polly to do some things, sometimes she gets it right but sometimes she gets it wrong. For example, if you ask Polly to sit down but she jumps instead, say "No, sit down" or if she gets it right say "yes, that's right". Encourage the child to tell Polly if she has got it right or not.