DoubleYou

DoubleYou is an opener that starts with a T-Spin Single resulting in a W-shaped valley (thus the name). There are many ways to continue it, among others a C-Spin that can end in a Perfect Clear (pwn's STD).

Second Bag
Some ways of how a T-Spin Double might be stacked:

Some more advanced setups:

pwn's STD
The T-Spin Single can be also followed by a Triple Double Attack (C-Spin). This is also known as a Single Triple Double or short STD. This one was discovered by pwn_of_numbers:

This setup has 2 nice features. For one, twists can be used to stack the pieces in different orders.

Secondly, this setup can result in a Perfect Clear after 8 cleared lines in total. 72 % of all third bags can end in a Perfect Clear in theory (51 % with a T-Spin Single or Double beforehand). The first 2 solutions will work for around 57 % of all third bags each.

If Z piece comes early in third bag, then chances are pretty slim for a Perfect Clear. In this case, you can also try to build a T-Spin Triple or Trinity instead of the T-Spin Double.

Here's another STD. It will work, if I piece comes before S piece in the second bag. Unfortunately, the fourth line cannot be completely filled with the second bag, and there's no opportunity for a Perfect Clear.

T-Spin Triple
Here are some further ways to make a T-Spin Triple in the second bag. Most of them will make the TST at the very bottom and neither of them will result in a T-Slot at the start of the third bag.

The first 2 setups can end in a Perfect Clear after 4 further cleared lines. In case of the first setup, it may work for 95.7 % of all third bags whereas at least one PC pattern is always applicable if either L or J is among the first 2 pieces.

The second setup offers a Perfect Clear solution for 86.7 % of all third bags.

L & J mirrored
If the right side was already stacked in the first bag but L and J show up in the wrong order, then you can still try the following. Of course, it will have much less continuations (no STDs).

pwn's STD Analogon
In the following setup, the locations of the OSZT stack and LJ stack are switched whereas L & J are stacked mirrored. This setup has less continuations and it can prove problematic, if pieces appear in the wrong order in the second bag (L before Z). However, there's also a STD Attack with a chance for a Perfect Clear.

27 % of all third bags can result in a Perfect Clear after getting a T-Spin Single (or Double). This chance increases to 64 %, if ignoring the T-Spin line clear in the third bag.

Here's another STD attack whereas L is placed before Z in the second bag. No chance for a Perfect Clear this time and the resulting field is pretty messed up. This messiness can be fixed by stacking for a further T-Spin Triple.