Source: ABF youth bulletins

Take a look at this problem:

Jumping to 3NT may be your first instinct, but this is a bit premature. Imagine if partner has these type of hands:

(a) Spade Suit Kx Heart Suit Jxx Diamond Suit xx club suit AQJxxx Opposite this minimum hand, 5club suit is a much better contract.

(b) Spade Suit Kx Heart Suit xxx Diamond Suit Ax club suit AQxxxx Opposite this hand, 3NT is cold but 6club suit is also cold!

Essentially, with so many different possibilities, we must at least try and see whether 5club suitor even 6club suit is a possibility before we commit to 3NT. How do we do this? A very well-known convention, also known as the Bourke Relay, will help you out. When you have an uncontested auction of 1minor – 1Major – 2minor, use the next step bid as artificial and game-forcing. So in the auction above, that would be 2Diamond Suit . This would allow you and your partner to continue exchanging information about your hands until you both decide what the best contract is.

For example, imagine after rebidding 2Diamond Suit, your partner now rebids 2Heart Suit, suggesting four hearts. You can now bid 3club suit (cannot be passed out as we are in a game-forcing auction!) and your partner now rebids 3Spade Suit. What do you know? Your partner must be something like a 2=4=1=6 shape, and now you have the information that 3NT is likely down on a diamond lead! Not only that, 6club suit is starting to look like a real possibility!