Partner's hand was:
K Q 6 
Q 8 7 3 
K 6 5 
A 3 2 Additional agreement with Ron
Over <1 bid> - <1 bid> - 1N, responder bids as follows:
2C: New minor forcing with an invitational hand (even if 1C opened)
2D: New minor forcing to game
The details of Two way Checkback
2. Fourth suit forcing to game.
Typically bid after opener has opened a suit and rebid another. (1C - 1H - 1S)
Now responder bids the fourth suit (Diamonds) as an artificial game force.
Other jump bids by responder will be invitational
With the unbid suit controlled opener will bid NT else describe the hand further
It is to be noted that a further Western Q may be looking for a half stopper
3. Lebensohl over reverses
Typically bid after opener has reversed (1C - 1S - 2H) showing 16-21 points.
Now responder can bid 2N artificial similar to Lebensohl.
This allows responder to stop below game if he responded with a very weak hand.
After the sequence mentioned above,
2S would be non-forcing;
3 level bids will be game forcing;
2N will be a relay to 3C, opener will not accept the relay with 19+ pts
The details of Lebensohl over reverse
4. Checkback Stayman
Typically bid after opener has rebid 2N (1C - 1S - 2N) showing 18-19 points.
Now responder can bid 3C artificial similar to New Minor Forcing.
The details of Checkback after a jump to 2NT
"Unusual over unusual"
For example, partner opened 1H and opponents intervened with 2N for minors
You bid 3C (the lower suit) to show a limit raise for partner's suit
and 3D (the higher suit) to show a game force with 5 cards in the remaining suit (spades in this case).
A bid of 3H would be a minimum heart raise.
A bid of 3S would be natural, but non-forcing.