I have been training dogs for 20 years. In that time I have tweaked my programs to benefit the dogs and there owners.
Typically I advise dog parents to practice 10-15min per session. Those sessions should be repeated 3-5 times a day with an 1-2 hour break in between. You should still enforce commands in between the practice sessions to make training a lifestyle.
Now some things to consider:
Training should start when you bring the dog home for the first time. Whether your dog is a puppy or a rescue.
If your dog is 2-4 months of age you should start with crate and housebreaking.
The other things you can work on is name recognition and some basics like come, sit and place. Practice session should be short. 3-5min
This is something you should do periodically through out the day especially just relaxing in the living room. Once you have decided on a name let your puppy play and periodically say the name if he or she looks give your pup a treat. (Have a bag or container with you to be ready) wait till your puppy starts paying attention to something else and repeat. Continue to do this until you see your dog respond consistently.
This can be practiced with 1 person or multiple family members.
Your puppy should have a regular buckle collar around the neck. You have to control the head to guide the body. A standard leash 5-6ft long. I start off extra small leashes. (5 bucks on Amazon or at Walmart).They are very light and it will be easy for your pup to drag around.
When first introducing new commands it is best to do them in a distraction free environment. Once your pup understands the commands better then you can add distractions or change practice areas.
If you are working by yourself have the pup on leash and walk around. When your puppy goes ahead of you squat down and say come. When he comes have a treat ready.
If you are practicing with additional people then you want to do a really exercise. If you have 2 people just spread out about 6-8 feet. Have puppy go to each person back and forth. As you puppy gets a better understanding increase the distance. If you have more than 2 people create a triangle, circle or square and alternate from person to person.
If using treats have treat ready in fingers. Face your puppy and position your fingers above their nose and motion slowly from the nose to above there head. If dog tries to bite your fingers try using an audible correction like EH,EH. You might have to use a leash and also place your hand on their rear and try and help while saying “Sit”.
With leash in hand take a step or 2 backwards and say “Free”. You have to establish a release word to teach your dog to hold the commands.
Once you have established the sit you can now move on to Place.
Place is a command that uses a dog bed. Have your dog sit next to the dog bed. Have your pup on a leash and guide leash towards the dog bed, point to the bed and say “Place”. If your dog goes on to the bed give a treat and lots of verbal praise.
When it comes to older dogs you can use the same process above. You can increase the time to 10-15min.
Always start new commands in an environment free of distractions. Once your dog has mastered the commands start practicing in different environments. Backyard then front yard. Then try to enforce commands when you have guest come over or when you are outside and your dog sees another dog.
If your dog has a difficulty ignoring distractions while using food. Chances are your dog has a lot of energy and need to use a different method of training to help achieve success.
There are different techniques out there so do your research and find what fits for you.
Good luck in your training.