NEW YORK (Money) -- Tough financial questions come your way all the time.How much do I need to save? Should I buy or lease? Should I refinance my mortgage? It would sure be nice to have an easy guide on hand for those moments.Now you do.

1. For return on investment, the best home renovation is to upgrade an old bathroom. Kitchens come in second.

2. It's worth refinancing your mortgage when you can cut your interest rate by at least one point.

3. Spend no more than 21/2 times your income on a home. For a down payment, it's best to come up with at least 20%.

4. Your total housing payments should not exceed 28% of your gross income. Total debt payments should come in under 36%.

5. Never hire a roofer, driveway paver or chimney sweep who is going door to door.

6. All else being equal, the best place to invest is a 401(k). Once you've earned the full company match, max out a Roth IRA. Still have money to invest? Put more in your 401(k) or a traditional IRA.

7. To figure out what percentage of your money should be in stocks, subtract your age from 120.

8. Invest no more than 10% of your portfolio in your company stock - or any single company's stock, for that matter.

9. The most you should pay in annual fees for a mutual fund is 1% for a large-company stock fund, 1.3% for any other type of stock fund and 0.6% for a U.S. bond fund.

10. Aim to build a retirement nest egg that is 25 times the annual investment income you need. So if you want $40,000 a year to supplement Social Security and a pension, you must save $1 million.

11. If you don't understand how an investment works, don't buy it.

12. If you're not saving 10% of your salary, you aren't saving enough.

13. Keep three months' worth of living expenses in a bank savings account or a money-market fund for emergencies. If you have kids or rely on one income, make it sixmonths'.

14. Aim to accumulate enough money to pay for a third of your kids' college costs. You can borrow the rest or cover it from your income.

15. You need enough life insurance to replace at least five years of your salary - as much as 10 years if you have several young children or significant debts.

16. When you buy insurance, choose the highest deductible you can afford. It's the easiest way to lower your premium.

17. The best credit card is a no-fee rewards card that you pay in full every month. But if you carry a balance, high interest rates will wipe out the benefits.

18. The bestway to improve your credit score is to pay bills on time and to borrow no more than 30% of your available credit.

19. Anyone who calls or e-mails you asking for your Social Security number or information about your bank or credit-card account is a scam artist.

20. The best way to save money on a car is to buy a late-model used car and drive it until it's junk. A car loses 30% of its value in the first year.

21. Lease a new car or truck only if you plan to replace it within two or three years.

22. Resist the urge to buy the latest computer or other gadget as soon as it comes out. Wait three months and the price will be lower.

23. Buy airline tickets early because the cheapest fares are snapped up first. Most seats go on sale 11months in advance.

24. Don't redeem frequent-flier miles unless you can get more than a dollar's worth of air fare or other stuff for every 100 miles you spend.

25. When you shop for electronics, don't pay for an extended warranty. One exception: It's a laptop and the warranty is from the manufacturer.