1. Go to ADA.gov and look at the law defining what is a service dog and what isn't.
2. Get a dog with proper size for what you want it to do. If you need it to help you off the floor, that's a big dog.
3. Go to google on that interweb thingy, and search for dog training in your area. Call the ones you find.
4 . Ask them if they can help train a dog to be a service dog, with specific jobs that you want the dog to assist you with. What do you want the dog to do? If you plan on taking it out into public places, the dog should be very well trained, calm and not interact with other humans ( no jumping on people, not distracted by other dogs, follow commands and not be scared in like, a crowded mall, etc.) the ADA does not require certain sizes, but I wouldn't expect a chihuahua to help me off the floor or to break my fall.
If the trainer says he/ she can't do it, maybe they can get a part of the training done? Maybe doggie basic or good citizenship class. Maybe they know someone who can train a dog with your goals in mind. There is no required certification. You can train your own dog, if you know how, but I wouldn't recommend it, unless you are a trainer.
A well trained service dog sets a good standard for others and is well behaved in public. You should not take a puppy out dressed as a service dog.
Service dogs do not need identification cards. Or training certificates. Up in NY the trainer has to be certified.
It's not so hard.
If you can't afford it, maybe you could take up a collection. There are academies that offer free or reduced cost service dogs for those of low/no income, but the waiting list is 2-3 years long.

I have 3 dogs, all lab crosses, and the oldest one will come lay by me before I have a seizure. He also won't let anyone get near me

I have a privately trained SD. We found a largebreed hunting group dog that was a sweetheart and really took a liking to me. 5 months later, I was diagnosed "seizure disorder" the sweetie pie, was alerting me to seizures. My amazing wife, through contacts, found a trainer to work with us and to help us satisfy ADA requirements, and state requirements. With an exchange of services and referrals from me, we cut the fee, took 6 months to get the dog ready to go out in public. She's been a working dog for 9 months now. We go everywhere. I keep a fabric muzzle in my pocket and a water dish in my knapsack, and have thermo boots for hot pavement/ icy salty sidewalks. With creativity, you can get and develop a SD.

Hi Bob!
Food and praise are great motivators.
As for intelligence? I think eager to please. Size depends on what to want the dog to do. If you want the dog to brace so you can use its shoulders to help you off the floor, that would need a big dog. In public, they must behave. The ADA is not specific, people a used the term service animal, so now it is Service Dog.

I would like to know as well where can you take your dog for training. My schnauzer seems to be more aware. She even notified my husband when I was having a seizure in the tub. but taking her in public is a whole different ball game. However I do a Cane Corso mix pup that is very alert and stays on my heels and I would like to try and get one of them trained.