New York (CNN/Money) – By now, any family squirreling money away to send their kid to college has heard of 529 plans.

After all, since Kentucky opened the first such plan back in 1990, financial planners and other pros have been giving these state-sponsored savings vehicles a big A-plus. It's tough to argue otherwise.

The most enticing thing about 529 savings plans, of course, is that earnings are exempt from federal taxes if they're spent on college costs such as tuition, books and room and board from now until 2010, unless the current tax law is renewed. The plans are flexible, allowing families to change beneficiaries if one child decides to skip college and another gets accepted to a pricey Ivy League university. Moreover, they are open to anyone regardless of income. In fact, it's possible to stash a lot more money into a 529 plan than any other college-savings vehicle – up to $250,000 in some states.

But peer a little closer and you'll quickly find that some of the 47 college savings plans available today don't deserve the highest marks. They may charge exorbitant fees. Others place restrictions on when participants can withdraw their funds without paying a penalty. And some have better investment choices than others.

How do you make sure you've picked a plan that's worthy of the honor roll? Ask the following five questions before signing on:

It's easy to skip over the fine print that spells out how much a 529 plan actually costs. But those tiny details can take a big bite out of your savings. Example? Fees may include enrollment and maintenance charges, sales fees, management fees and penalties.

"There are so many different types of fees that are charged," said Chris Hunter, program manager at the National Association of State Treasurers, which tracks plans nationwide.

In Maryland, for example, individuals must pay a $90 enrollment fee just to get started. Illinois charges $75. Kentucky: $50. Some states, including Indiana, don't have an enrollment fee but many of the investments they offer come with one-time upfront sales fees or "loads" – as much as 5.75 percent.

After initial fees, "annual costs can run from as little as 0.35 percent up to 2.5 percent or more," said Hunter. "They're all over the map."

Individuals who opt for an out-of-state program may quickly find that plenty of 529s charge higher fees to non-resident contributors. For example, in Alabama, non-residents pay a yearly $25 maintenance fee; residents pay $10. The fee is waived for accounts that have a minimum $25,000 balance, a practice that's not uncommon.

Management fees also vary. Investing through a broker generally adds more expenses than buying directly into a plan.

Direct plans "may have a management fee and some enrollment fee but you would not have to pay a broker," Hunter notes. "And in most states, these are cheaper than plans where you go through a broker."

Plans also may have minimum contribution levels, which usually are reasonable. Still, it pays to ensure you can keep up with the required deposits. The Wyoming College Achievement Plan has an initial minimum deposit of $1,000 and subsequent payments must be $50 or more. (The minimum deposit amount for locals is just $250.) Other state minimums tend to be cheaper – about $300 annually.

Each 529 offers its own set of investment choices and it's important to know what your options will be before you pick a plan.

Most states offer age-based investments. Money will be invested in riskier, equity funds for young kids who've got years before they go to college. As kids approach college age, savings are shifted to less-risky plays.

"One of the things that custodians need to be concerned about is how much time before the student needs the money," said K.C. Dempster, co-author of "New Strategies for College Funding" and director of program development at College Money, a Marlton, N.J., firm that focuses on financial planning for college.

Age-based portfolios tend to be better for older students because they're invested conservatively, says Dempster.

"However, if children are a lot younger, I'd caution parents looking at the age-based mix of equities and bonds. College inflation has been running almost double the rate of regular inflation for 30 years and age-based portfolios lean toward the more conservative side, so you might not get the returns you need."

Because 529 plans are relatively new, check on the fund managers' reputations when picking one. You can find out who the fund manger is by going to state program Web sites or by calling their customer service reps. And research your investment choices on a site like Morningstar.

The 2001 Tax Relief Act did away with federal taxes on 529 earnings when used for college costs. But only 23 states have followed the federal government's lead. Many still tax earnings from their plans.

On the other hand, some states, like Kansas, waive taxes on earnings their residents reap by investing in out-of-state 529 plans. Other states, such as Colorado,Illinois andNew York, allow residents to deduct their contributions. Some offer a mix of tax perks.

In other words, it pays to shop around.

That's what David Debut did. After looking about, the Virginia resident opted for his own state's 529 plan because it allows him to deduct $2,000 per account – a total of $6,000 for his three children. That saves him some $345 a year in state taxes. And even though Virginia charges a hefty $85 enrollment fee, Debut liked the fact that expenses were low – from .85 percent to 1 percent.

The new tax law passed last year made it much easier to move from one state 529 to another. Nevertheless, that doesn't mean the plans themselves have followed suit. A handful of them penalize individuals who withdraw or move money within a certain period of time.

For example, earnings taken out of the New York plan in the first three years will be hit with a 10 percent penalty. In Utah, individuals who withdraw money in the first two years to pay for non-college expenses must forfeit all their earnings. And earnings must remain untapped in a Georgia 529 plan for one year or they're subject to state income tax when withdrawn. (After that, the state doesn't tax earnings.)

Families on a tighter budget may have another reason to choose a 529. In some places, states will match their contributions, much like employers do with a 401(k) plan.

Louisiana's Student Tuition Assistance and Revenue Trust Program for example, matches 2 to 14 percent of residents' contributions to their 529s. Matching funds are capped on a formula but it's possible for a family with a high school senior to get as much $50,000 in matching grants this year. Those who earn less than $30,000 per year qualify for the full 14 percent matching grant, but 2 percent grants are given to individuals who earn $100,000 or more. In addition, Louisiana gives state tax deductions up to $2,400 per child per year to those who contribute to the 529 program.

Michigan also gives matching grants -- about $1 for every $3 a family invests -- up to $200 to families whose federal adjusted gross income is $80,000 or less and who have a child 6 or under

Given the differences in 529 plans, experts say it pays to shop around. While there are incentives for families to start saving in them, individual plans may or may not meet your needs.

The Internet makes it relatively easy to shop around. Check out Web sites like Savingforcollege.com and the College Savings Plan Network.