The trick in this game is to build lots of long chains (no loops!), then give away small section to your opponent. The most important thing to remember is to give away the last two cells of any significant run.

Assume you're near the end of a game, nobody has any moves they can make without giving away some squares. Additionally, all the small one or two square chunks are gone. There's nothing left but really long chains. It's your turn and you've just about done with one of those chains:

|A |A |  1  2
Where do you go now? Do you draw the line at 1 so you can take the remaining two squares?

No! Draw your line at 2 so your opponent can take those two, and then is forced to open the next chain for you!