Puppy class is a must IMO, it is lots of fun and teaches the puppy a lot and helps with socialization.
Recalls should be one of the most important things. I start right away with baby puppies calling their name and running backwards, having them chase me and they get a treat for coming.
Choose a word, like come, and when they respond, they get rewarded, lots of praise, and it is very fun. Always keep it fun and exciting and do it at random times in the day, b/c puppy attention spans are almost non-existant.
Play hide and seek and call the puppy to find you, really easy stuff that teaches the puppy to come when you call. That builds a good foundation and helps the puppy know when you say come, it is a fun and good thing to do so.
Maybe you call the puppy to come and start playing a fun game, like fetch or tug. Maybe you call puppy to come when you bring home a new toy or bone. Come is always a good thing, never tell the puppy to come for things that the puppy doesn't like, like nail trimmings or bathes or stuff like that, keep it always happy while they are so young.
You can also play a recall game, where people stand in a circle and call the puppy individually and when the puppy comes to them, puppy gets lots of praise, petting, and a treat or toy.
Now the the stay the recall and then front is a little harder, I would wait until at the very least 6 months to start teaching those things, and just focus on all happy, good, and easy things and set the puppy up to succeed while young.
The puppy stage is a favorite of mine. Enjoy this time, it is going to fly too fast....