1. Don't buy on credit except for a house, and pay your CC off in full every month.
2. Save at least 10% of your income every month.
3. Get a few months rainy day fund set aside in savings, then max your IRAs or 401Ks every year.
4. Save anything else in a taxable account.
5. Stick to low cost Fidelity or Vanguard mutual fund tied to the S&P 500.
6. Don't touch your investments until you're close to retirement and need to rebalance.

There's obviously a million additional things, but these are the best things most people could do.