On the bells - we use them, and they work. Pluto lets us know when he has to go.
On the training, just wanted to chime in that Pluto always does better with positive reinforcement - so I would agree with one of the other posters about not punishing or disciplining outside of timeouts - get them to do what you want (good behaviors) through reinforcement.
Example - If they are mouthing, get them to stop buy training them that they get treats when they don't mouth. A puppy training class is money well spent!
Just like kids, you have to redirect a lot - but redirection works really well. For both kids and dogs and training can be fun.
Good luck in whatever you do.