There is no excuse for not saving for your future. None.

No one will do it for you, and, besides, investing for your retirement has never been easier. Pick a tax-advantaged plan, contribute the maximum allowed, then sit back and watch your money grow.

OK, it’s a little more complicated than that. You’ll want to keep track of your all-important asset allocation, but even that’s gotten simpler. You’ll have to have the discipline to start early and stay the course even in tough times. And you’ll have to have the willpower to leave the money alone.

Try running the numbers on MSN Money’s retirement calculator to find out where you stand.

401(k): It’s painless and pretax
Most people save through payroll-deduction plans that put off a date with the tax man until their golden years. The most common is the 401(k).

A newer alternative, the Roth 401(k), does the opposite, allowing you to invest taxed income and withdraw the earnings tax-free. (See Avoiding taxes with a Roth 401(k) on MSN Money Video.)

Sign up as soon as you can. Start setting aside at least $4,000 a year at age 25 and you’ll have more than a cool million 40 years later. Wait 10 years and you’ll have less than half of that. (See “Why bad 401(k) advice is better than none.”)

Take advantage of every dollar of 401(k) matching money your employer provides. Large companies typically match 50% of your contribution, up to 6% of your gross pay.

Consider investing in both a traditional 401(k) and a Roth 401(k). The contribution limit for 401(k)s — about $15,500 — applies to the combined contribution. (See “Build a bigger nest egg.”)

A Roth 401(k) is particularly beneficial to those who anticipate a higher tax rate in retirement and young workers new to the work force. (See “6 simple rules for retiring wealthy.”)

More employers are making 401(k) enrollment automatic for all employees. But don’t leave investment decisions to your employer, who may deduct too little and invest it too conservatively. (See “7 hot 401(k) trends.”)

Don’t quit contributing to your 401(k) during tough economic times. (See “6 smart 401(k) moves for rough times.”)

If you’re a teacher or an employee of a nonprofit, your 403(b) plan may not have an employer match and may have high fees. An individual retirement account, or IRA, might be a better option despite a much lower contribution limit.

Allocate appropriately
Asset allocation is crucial when investing your retirement savings. Your employer likely offers a dozen or more investment choices. You want a mix of stock funds, bond funds and cash equivalents that maximizes your earnings within your acceptable level of risk.

Younger workers have time to recover from stock market downturns and are advised to invest heavily in stock funds, which generally produce the greatest yields. Experts recommend a stock allocation of no less than 60% to 80%. For those nearing retirement, movement toward bond funds protects investments from market volatility.

Diversify, diversify, diversify. Select at least three non-overlapping stock funds, possibly a large-cap, a small-cap and an international stock fund. Do so after comparing fund performance and fees. (See “Build a stable retirement portfolio.”)

Your plan may offer investment guidance or help in another form: So-called lifestyle and life-cycle funds offer an asset mix based on your age, goals and risk tolerance. No two funds are alike, so compare diversification, risk and fees.

Don’t tie up your money in your employer’s stock. If your employer’s match is company stock, invest your contribution elsewhere. (See “7 ways to mess up your 401(k).”)

Review your asset allocation at least once a year.
Keep your mitts off the money
Never cash out your 401(k) when you change jobs. You’ll pay taxes and penalties and deprive yourself of future earnings on the money. Roll it over to an IRA or your new employer’s plan, or, if possible, consider leaving it where it is. (See “Leaving a job? What about that 401(k)?”)

401(k)s between $1,000 and $5,000 will be automatically rolled over to an IRA when the worker leaves a job unless the worker makes other arrangements.

Make sure any rollover is direct and is completed within 60 days to avoid taxes and penalties.

Resist the temptation to borrow from your 401(k). Not only will you reduce its earnings, you’ll immediately have to repay the loan or face taxes and penalties if you lose your job.

If you absolutely must borrow, some employers have begun to offer 401(k) debit cards that take away some of the risks. (See “A 401(k) debit card? It’s not so bad.”)

Move to the next level
If your employer doesn’t offer a plan, the most common options for retirement savings are the traditional and Roth IRAs. IRAs are worth exploring even if you’ve taken full advantage of your employer’s plan.

Look into high-yield bonds or commodities that may not be offered for your 401(k).

Timing is everything. You could make an additional $40,000 over 30 years if you deposit $4,000 in your IRA at the beginning of each tax year rather than the end.

Converting a traditional IRA to a Roth to get those tax-free payouts comes with costs: You’ll have to pay taxes on your pretax contributions and earnings. You can stretch out the conversion over time to reduce the immediate tax bite. Use MSN Money’s Roth IRA Calculator to decide whether converting is a good idea. (See “Why you need a Roth IRA.”)

You’ve maxed out your contributions to a 401(k) and IRA, and you still have money to invest?

Index funds have lower fees and generally outperform actively managed funds in the long run.

Think about tax consequences when investing in non-tax-advantaged funds. Good bets for a favorable tax rate include stocks, index mutual funds and tax-efficient mutual funds. (See “5 ways to be a tax-smart investor.”)

Variable annuities are an unattractive savings method for multiple reasons, including high fees and tax treatment. (See “The worst retirement investment you can make.”)

If you’re among the declining number of people who have a traditional pension but you don’t know how to access it, the Pension Benefit Guaranty Corp. can help you. (See “Track down your long-lost pension money.”) The National Registry of Unclaimed Retirement Benefits can help you find 401(k)s.

MSN Money