Jumping up can seem cute when a puppy does it but it's not as fun when when that puppy grows into a full sized dog and is almost knocking you, your family and strangers over with their greetings. As with most unwanted behaviours, it's best to start teaching your puppy not to jump up as early as possible to avoid it becoming a problem into adulthood.
Stopping this behaviour is as simple as-
Ignore jumping up
The main reason puppies jump up is for attention. Therefore the best way to stop them doing this is to avoid giving them the attention that they want. This means completely ignoring them when they jump up. This also includes telling them off, touching them or even looking at them. To puppies these are all rewards and by doing these things you are encouraging them to carry on jumping up.
Reward four paws on the ground
Only praise and reward your pup when they have all four paws on the ground. This can be as simple as bending down to their height and stroking them or talking to them.
Consistency is key
Remain consistent with your approach and they will soon learn that jumping means no attention, whereas staying on the ground means rewards. Consistency also means involving everyone in the household and any regular visitors in your approach to avoid your puppy becoming confused.
If your puppy continues
Some puppies will take longer to understand the rules than others, especially if they've previously been given attention for jumping up.
In some circumstances they make increase their jumping as a way of trying to get attention because they don't understand the change in rules.
As long as you and the rest of your household stays consistent, your puppy will eventually understand that jumping up no longer gets them attention.
It can require a lot of patience but it will be worth it so persevere!
Jumping up when scared
Puppies and dogs will also sometimes jump up when scared or stressed. This is different to the normal kind of jumping up for attention and it's best to respond to your dog when they do this. Give them some reassurance and remove them from the situation if possible.