Short answers:
Read, Count, Time, Answer whys, Allowance.
Details below:
Read: From the beginning, read. Baby brains have more brain cells than adults. The first 2 years the brain removes useless brain cells. If the brain knows words are important, it keeps them. It is why some people can never learn to speak like a foreign language like a native, they just do not have the brain cells to properly hear the sounds they are messing up. I have been told Japanese does not have an ‘L’ sound.
My kids could read before they started kindergarten. Not very well, but each could read their favorite book.
Corollary is to practice letters. It is not enough to have the letter chart on the wall, read them off.
Count: Similar to reading. Start as early as possible. Although I am sure there are exceptions, they have found that most kids, if they are good at math at the age of 5, are good at 10, 15, and 20. Likewise if they are bad, they never catch up.
Whys: You never want them to decide they cannot answer a question. Work hard at coming up with appropriate answers that are accurate. Occasionally toss in a ‘I do not know, why do you think it is?’. Later add more questions to spur thinking. ‘Why is the grass green’ I have often asked.
Time: Your kids will and do value your time with them, not the money you spend on them.
Allowance: I have seen many people struggle with finances. In the Majority (not all) cases, their childhood did not involve an allowance, they would just get things if their parents felt they could afford it.
When they are old enough, start giving an allowance. We did it with no chores expected. Chores are what you do because you are a family member, not because we pay you. When you go somewhere and they want a 'frozen lemonade' or a trinket, tell them they are welcome to it, with THEIR money. It is interesting to see how often the NEED disappears.
My son and I were at a festival when he was 7 or 8. I typically have a refillable water bottle with me. Now this was in Florida and it was a hot day. My son turned to me, clutching his throat, ‘Oh dad I am so parched’. I was impressed I did not know he knew the word ‘parched’. Me: ‘Oh that is so sad’ with a concerned look on my face, ‘what can we do about that?’ Son: (stammering for emphasis) ‘I, I think, I need a lemonade…’. Me (faked surprised look on face as I notice the frozen lemonade stand we just walked by) ‘That is a great idea, I think you should’. Son, with the biggest grin I had ever seen on his face, turned around to walk back to the frozen lemonade stand. He had only taken one step to the stand, when I added ‘with your money’. He stopped dead in his tracks. OMG you could see his brain contemplating what to do. He turned around and in a very casual voice, ‘Hey dad can I borrow your water bottle’. At that point I knew he valued money appropriately.
When I first planned out the allowance, I contemplated the alternative solution, which I had seen others play out. In the late teens, early twenties, many friends had to call their parents and beg for money to cover 3 months of rent (2 late and current). So far so good, I have saved money by providing an allowance.