It's important that you find a SAR dog organisation near you to help with training but in the absence of that...
Start by getting the dog interested in Something. Most SAR handlers use balls or a tangible toy (e.g. tug rope) but there's no reason you can't start with food or praise if they work better for you. Long term you want to be moving onto a physical reward like a toy as the problem with training with food is that dogs get full
Once you've got the dog interested in the Thing then start using the Thing as a reward for training. For example Echo goes nuts for solid rubber balls so I use them as the reward to keep her focus on me. If she starts to get distracted or lose track of what I'm trying to teach her I show her the reward again (where show means waft under her nose) and give her a more basic command she can do easily (e.g. sit). I reward that command, remind her what she's working for and go back to where we were more slowly.
You'll soon find that your dog will know that when the Thing comes out he/she is expected to do two things:
1) Pay attention to you.
2) Follow your instruction and in doing so get a fun reward.
Now you're ready to get the dog searching for people. It's at this point you realise you don't have anywhere enough friends as you don't want to use the same people each time. Get your volunteer to take the Thing, show it to the dog and run off a short distance. Hold the dog back and release him/her with your chosen search command e.g. "search", "go search, "find", "go find", "sasquatch", whatever you choose. The word shouldn't sound too much like another command you use in training, I chose to use 'go find' as 'search' starts the same as 'sit'. Your mileage may vary.
If the dog is excited enough he/she will barrel off down the track to your friend and as soon as he/she gets within arms length your friend should reward the dog. Balls should be thrown, tug ropes should be pulled and praise should be given.
Each time he/she appears to have got it make it slightly more complicated, maybe a slight increase in distance or get your friend to hide out of sight. If he/she gets confused just back off the training to a level they're comfortable with and rinse/repeat.
Repeat until he/she can find a good array of friends flawlessly
And remember the thing that everyone (including me) forgets: More short training sessions, not fewer longer training sessions. Give your dog time to think about the training rather than just workworkwork.