In the bottom left corner of your main screen you will find the Dot Meters.  The top one is the Hunger Meter, the lower one is the Happiness Meter.  Both Meters start empty and as you interact with your Dot, they will begin to fill up until they go completely green as in the above illustration.

The Meters have recently been decoupled from the old Points system and now fill at a constant rate per Dot interaction (Dotnip and Dewdrop excepted as you will see in he breakdown).

Each Meter requires you to interact 3 times to fill them.  When you interact with your Dot involving certain activities, you will gain Dot Growth XP and also start filling the Meter/s.  Once full, each Meter will reward you with an additional 30 Dot Growth XP. 

The Fullness Meter is simply a case of feeding your Dot with the various food types available 3 times.  The Attention Meter is slightly different and can be filled by carrying out any of the following activities with your Dot (again, 3 times):

• Feeding Dotnip to your Dot
• Petting your Dot
• Playing Fetch with your Dot

Feeding Dotnip is a little different in that the Attention Meter filling is completed, no matter what the current level is and you will gain an instant 90 Dot Growth XP, plus a Bonus of 30 Dot Growth XP for filling the Meter (120 total). 

Below is a full breakdown of how the Hunger and Attention Meters fill up with each activity and also the Dot Growth XP you will have earned (from the various activities) whilst filling them up:

The values assume that you didn't get any Dot Growth Bonus from completing Trick Training or by completing Dot Desires (which are additional to all of the above).