Puppies are like sponges! They are learning every waking moment. It's such a joy to watch and exhausting to experience.
For a puppy to be able to respond to your requests for sit, down, stay, come - anything really - requires lots of practice in many different environments. Practicing in the kitchen is great for the very first few times but then you need to take it on the road and practice in other locations.
Difficulty is gradually increased so that the puppy is successful at each step of the learning process.
 
Progression can be something like this: kitchen, family room, basement, backyard, front yard, down the street, park (no kids or other distractions), parking lot, etc. The idea is for the pup to know that sit means sit regardless of where he is.
 
Little Dora, 3 months old, is putting together "follow me, touch, sit" for the first time. Not too bad for the first time! We need to work a bit on a straighter sit (parallel to her owner) but she's pretty darn good. She is in the backyard with few distractions.