I would do it in this order.
The most "legend" (Green -> and then the lower colours)
Go for the one with N/A in the SPLIP column, meaning it's between physical files.
If it's just after a shift of VTS (like in the example LUK gave you)
Somewhere close to 50/50
If you see the another color other than green you will end up with something that has video in it. Try to select the first one (the start of the video) rather than in the middle of the video of the same VTS. If you need to pick one in the middle of the video, play the stuff and see how "disturbing" it would be with a slightly pause there (where the laser switches layer).
If you player supports it, enable the Seamless option that you see in the upcoming build windows (after you have selected on layer break point here) you should not notice the layer break at all, even if it's in the middle of the video. Most modern players support that function. You can burn one that you know have the layer break in the video and when it plays over the layer break you will notice if you can spot the switch or not on your TV.