I'm no way an expert, and I'm still going through the "transition" so to speak.
However, I have been doing this a few months, so I'll give you some advice.

When I first started, I dipped into the words quite often.I would go into passages just for the heck of it, with no real goal.

One day, I realised that it was all about purpose.This realisation was probably some kind of spontaneous activation.You know, that "aha" experience, when you finally just "get it."

I decided that I wouldn't bother ever photoreading again if I didn't have some kind of end goal/purpose.This helped tremendously.It focused me, and the activation went to so much better.

What you'll find, is that when you first start activating, you'll dip more, and probably read stuff that you think is relevant now, but in fact you could probably do without.That's normal, it'll change.

I'll tell you something GnarlyOcelot.I've photoread books and not needed hardly any activation in order to make sense of those books.This is completely different from when I first started.I used to worry about missing stuff.

I no longer worry about missing stuff.In fact, it's like the inner mind is directing me where to go, I just follow, like on autopilot.Very strange, but I've accepted that if that's how it is, then that's how it is.If it works, then it works.

Just stick with it.Gradually, you'll just know where to dip, you'll be on autopilot.
That's when you'll realise the power that the photoreading process gives.

Happy photoreading.