I'm so glad that worked for you! I felt like such a dope the first time I did it and realized it worked too. I've had been jumping staring off into the trees for years! Glad we all could help you. It really is a great forum for problem solving.
The best way to learn when the horse is going to take off is to set up your jump in a small course of trot/canter poles (depending on the pace you're jumping from). That way the horse has it's strides set up for it, and you know plainly when you'll be jumping. It also helps with teaching you to see a stride. I would be very wary with looking at the jump as a learner though - where you look changes the way you sit and balance, and as they say "look where you want to go" (i.e. If you keep staring at the jump you might end up on it!). The less generous horses out there can start refusing if you continually focus on the jump rather than the line and the rhythm and balance of your pace.
Edit: My instructor actually used to teach us an exercise where we had to jump with our eyes closed once we were on the line, to concentrate on the rhythm rather than the jump itself. That's a really good one for later down the line when you have a bit more confidence and balance jumping, as it shows you that you don;t actually need to see the jump and anticipate it to ride it in a balanced way.
Count, count, count the strides all the way up to the fence. It will keep you in rhythm with the horse the whole way there. It helps you figure out when the horse gets to the base and is about to take off. If you have an incredibly lazy horse (*herm*, like mine) that rather enjoys taking long spots just to throw you off guard, counting helps you tremendously.
Also, never ever ever look down or stare at the jump WHILE actually going over the fence. While riding, never look where you don't want to go. Horses pick up on this. Keep your eyes up at where you want to go! Good luck ;)
It is actually proved that upper level riders look at the top pole of the fence for at least 3 seconds on the approach. This is how long it takes your brain to process all the information about the jump. Once the jump disappears between your horses ears, then look over it.