Karen, I'm sure you will be given advice from more experienced people than me but for what it's worth here is some advice that I have been given by a few of the experts.
Peter told me once that once a dog is in a hyper active state they need to be re-focused. You need to put her back on the lead and do some basic training, such as heal work and sit. Once her focus is back on you, you can let her go again. If like Maggie, Domino is uninterested in treats on a walk then you can use a favourite toy to get her focus back on you. He also told me that I need to keep Maggie within her range of obedience. ie: if I let her go to far then she won't listen so call her back before she goes too far. A while ago she chased some ducks which were at the far end of a field I walk across. I can keep her from going over in that direction if I call her back before she is out of my control range and she is very obedient, but if I let her go too far I have no hope. I often keep a ball in my pocket and if Maggie looks like she has picked up on something and is not listening then I call her and show her the ball - she zooms back, she has a quick play and then is told to get on.
Ali also told me once that playing hide and seek will make them keep more of an eye on you. It's easy to do this time of year because of the long grass. It's the element of surprise I think. If Domino isn't quite sure when you might just disappear she is more likely to keep with you. I found this really worked when Maggie was younger. You can also try just changing direction now and again. Even walking back the way you came until she zooms in front of you then turn back.
I still have problems with Maggie but she has improved and does watch me most of the time!
