STAYMAN vs TRANSFER

As you know, after an opening of 1NT you should use the conventional responses of 2C (Stayman) or 2D & 2H  (Transfers). But which one? And when? To keep it simple:
1)   With only 4 card Majors use 2C - Stayman.
2)   With 5+ card Majors use 2D/2H - Transfers.
It really is that simple. You will either follow these bids up with a PASS (10 or less HCP), or an invitational 2NT (11-12, 5 card Major), an invitational 3 Major (10 - 12, 6+ card Major) or the game bids of 3NT (13  - 17 5cM) or 4 Major (13 - 17 6+cM). With 18+ you should be slamming. This structure is fairly immutable and needs to become second nature.
The responding hands that tend to be problematic are those that have 5 - 4 in the majors and are weak (less than 10). Now what? If you Stayman (2C) and  partner comes back 2D (they always bloody do!) what then? What do 2H or 2S mean? Even worse is when you have a GOOD hand, 5-4 in the Majors, you bid 2C and hear 2D. Now what does 3H or 3S mean? To be fair, there are complex agreements that cover these hands but they're not really necessary. What you do is with game-ish hands you transfer into the 5 c suit and then bid the other one. But what do you do with a dog like this?
Qxxx
Qxxxx
Kx
xx

When partner opens 1NT they will (mostly!) have either 2, 3 or 4 H's. Three possibilities. Two of which give you the longed for 8 card fit. So you have a 66% chance of being OK when you transfer. In Bridge terms this is almost perfect. Yes, sometimes partner will have 2 H's and 4 S's. This probability is about 10%. Not worth considering. So with the above example ALWAYS transfer into the 5 card Major and then PASS. Don't think about it - do it. KISS (Keep It Simple, Stupid)

A DIGRESSION
It is a principle of faith for me that I will always open 1NT with ALL 5332 shape hands with 12-14 HCP. Even if that 5 card suit is a Major. Every time. I would urge you all to do the same. Every time. With one tiny exception: if your major suit looks like this -  AKQJ10, you can open it and re-bid it. But do let me know when you get this 12 - 14HCP, 5332 hand. It is phenomenally rare. 2%? of 60 trillion? Nah, you do the math...