
I don't know any of the background information of your dog, but if it does happen again before you go to see the vet, stay calm and talk quietly to him as the others have said. Try to keep anything he could injure himself on out of the way. When he's coming round, he'll be confused, so turn off the TV/radio etc, just let him hear your voice.
I know it's easier said than done - I've never seen a dog fitting, but had a cat with epilepsy, and it's horrible to see.
I hope everything works out for you and your dog.
Take care
Lisa