Causes for a dog to have a seizure and remedies?

My 4 year old golden retriever, labrador mix has never had any health problems. Two nights ago he had what was diagnosed as a grand mal seizure. He seems to be okay but I am trying to get as much information as possible on it. This was the first and I hope for it to be last seizure, but just in case I want to be prepared. What known causes are there for seizures and what remedies can anyone suggest?