Right, here's what I posted, adapted appropriately I hope (but apologies if I've missed anything - oh, and please substitute she for he!). The dog I wrote the post about originally was prescribed Phenobarbitrate, as my own is, and I'm assuming that yours is too - please correct me if I'm wrong here.
Keep a diary day to day, including walks, fits, food, treats, stresses and stimuli and visitors/anything out of the usual in the dog's environment, thus try to identify any triggers. Change the dogs diet immediately if necessary and at once to one which has no colourings, preservatives or additives as they are big epi triggers. I use Fish4Dogs (available via their website) have in the past fed Naturediet which is just as good but more expensive and bulky to store, others feed raw.
Keep all stress to an absolute minimum. If pooch gets hyper around DC, keep DC away, likewise other visitors. If the hoover troubles her, put her out the way before you use it and soforth.
Keep her away from chemicals too, especially pine scented ones and avoid all pine scent in general if poss as this has beem proven to trigger. Some dogs will fit around the full moon - this is accepted by leading experts in epilepsy though not really understood and of course there's not much you can do but it's worth noting so your parents can keep an especial eye out during this time. Keep her away from/remove from her area computers too as they can trigger fits (it's believed to be the noise).
If she fits, stay calm, remove anything and anyone from the area she can get hurt by or could hurt or get stressed by, there's no need to panic or have any more than one person with pooch. Note the time striaght away and get her into the vet immediately if she fits for more than 5 minutes. Assuming she doesn't she should be able to have another Pheno with some food, most cases this is appropriate but I am NOT a vet only a rescuer so get the vets okay on this. It will depend on the dosage she is on, most vets will ok it as they normally start off on the lowest theraputic dose. (Pheno can cause liver damage long-term so the ideal is the minimum theraputic dose but sometimes this takes a while to identify and thus stabilise the dog onto a suitable dose). Upon coming round offer a small amount of food and a drink and fresh air - heat can be both a trigger and an added problem when a dog has fitted - but remember that she may be disoriented, may not know how you are and thus be unpredictable and may as a result try to bolt or get through a window. If in any doubt take into the garden only on a lead, you do not want a post-fit, disoriented dog escaping.
Have you noticed any "absences" or unusual behaviour such as pacing or excessive panting. Absences are when the dog appears "not with it", she may be staring at a wall, bump into things, be unresponsive to you. If so the immediate way to try to prevent a full blown fit is to apply compression to the eye area. Doesn't always work but often does. Also if so the vet might prescribe Gabapentin - some don't like to as it's not so well used here but is pretty standard for absences in the US, where they are far more up on canine epilepsy than the UK. Rectal valium would be a good thing to have on standby too.
Remember too that many vets are, IME and that of the rescue I work closely with and that has a very good reputation for it's care of epi dogs amongst other rescues, not necesarily very well versed/experienced in canine epilepsy and so it may be the case that you feel the need to ask around for a recommendation of a more experienced surgery (rescue is always a good place to start, as are dog forums like DogPages which has a lot of very dedicated and knowledgable owners and rescues as members).
The man who knows more than anyone else I know on canine epilepsy is Dave of Poplar Farm Rescue Kennels. He's the "real" owner of my current (foster) epi dog, an 8 yo GSD. He will happily give you as much help and support as possible. I'd really recommend that you either post on the forum in that link (he reads and posts on it each day) or send him an email (tell him you were recommended to talk to him by a Mumsnetter and he'll know it's me who suggested it!). At a rough guess I'd say he currently has about 8 or 10 epi dogs out of the 60 or so in the rescue.
Simple things too that you might not think of - always carry your vets number on your mobile and always carry your mobile when out with pooch, never ever allow her to swim... swimming was a trigger for my first epi dog but regardless you DON'T want a dog to fit whilst in water, she will drown. Don't get her too excited when in the company of other dogs. Make sure that ALL the family know what to do if she fits, even just so that they know to clear the room and leave you to it.
How often is your dog being medicated? And IS he on Pheno? As I said, I'm NOT a vet but if the meds are being absorbed rapidly it sounds possible that th dose might need to be split so that instead of, say, every 12 hours, you're medicating every 8 hours. Be careful too to ensure that you don't miss a dose or run late with medicating, especially if he's on Pheno, as this could really make a difference.
Again, I'd really, really recommend that you contact Dave at Poplar Farm, and if I can ever help in any way, just shout.