Characteristics of good starting combos:

• start with multiple line clears (doubles, triples, tetrises)
• do successive line clears (with 1 or 2 exceptions)
• end with single line clears

Note, that it is very hard to get a 10 combo, when you start your combo with a single line clear as shown in the video. Next piece would have been a yellow O piece, which always allows you to begin with a Double (when going for 2 wide combos). Another way to start with a multiple line clear is to have a small ledge at the bottom.

Here a table of sent lines by combos at the beginning of a match:

1 -> 0 | 0
2 -> 1 | 1
3 -> 1 | 2
4 -> 1 | 3
5 -> 2 | 5
6 -> 2 | 7
7 -> 3 | 10
8 -> 5 | 15
9 -> 7 | 22
10-> 9 | 31
11->11 | 42
12->11 | 53

How to read the numbers: When your combo counter reaches 12, you send further 11 lines, which sums up to 53 lines in total (plus some lines for doubles, triples, tetrises).

Me? I can do the theories, but others can perform much better in practice. And I just changed my spawning orientations. All I can do now is James Clewett.

I have somewhere a video of the only 12 combo, I did so far, but it's 1-key finesse and only 15 seconds long, so no good illustrative material. If somebody still wants to see it, then shout.