Student-loan debt in the U.S. passed the $1.5 trillion mark last year, making it our second-largest source of consumer debt, behind only mortgages. That's a disturbing trend for parents and college-bound children.

However, there is one morsel of good news: Parents seem to be more aware of the student-loan problem, and they're saving more to compensate. In an annual study of the savings habits of parents, Sallie Mae -- one of the largest student-loan originators -- found parents saved the most in 2017, the most recent year for which data is available, since the study began in 2013. The average amount saved in 2017 was $18,135, 11% higher than in 2016.

The healthy economy and high employment rate surely had something to do with this ... but not all. Sallie Mae's study highlighted several smart habits of successful savers. Here are five things you, too, can do.

Jar labeled "college" and stuffed full of paper money

Finding money to save for college isn't easy. Image source: Getty Images.

1. Make regular deposits

Six in 10 parents make regular deposits to their college savings accounts, according to the Sallie Mae study. This makes sense, as contributing regularly to any investment account is a surefire way to give the savings a boost -- in fact, I'm surprised only about 60% of parents do this. Of course, there are any number of daily expenses that get in the way of regularly saving.

What helps is to automate the process -- having a little bit of each paycheck swept automatically into a 529 college savings account, for example. (There are many places to save for college, and the 529 is just one, but it's also one of the most popular.)

Automating your contributions is a busy parent's best strategy. No thinking is required, no action is needed once it's set up, and you get used to living without that money over time. If you haven't done this already, take a cue from the successful savers mentioned in the Sallie Mae study and get it going. You can check with your state's 529 plan about setting up automatic contributions.

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2. Get a side hustle, or work more to save more

It's a sign of the times: Four in 10 Americans surveyed by last year have a side hustle or a second job. Sallie Mae found that nearly one-fourth of its survey respondents were working more hours to increase their income. There's definitely something to having a side hustle or working more, if it means a little extra in your child's college savings account.

3. Bank your rewards

This is an often overlooked idea for saving for college. Sallie Mae found "more than 1 in 10 (parents) put the cash back" from a credit-card rewards program into an account earmarked for college. That's genius -- I've always used my rewards for a gift card to Chili's. (Oh well, there goes date night.)

A few credit cards make this easier, but the concept is the same: Opt for the cash back, and deposit it into the college fund. True, cash-back rewards won't add up enough on their own to pay for college, but every bit counts, and this is a simple and effective way to add a little extra to Junior's account.

4. Spend less

This is an obvious one, but it doesn't hurt to reinforce it: Spending less on material goods, or cutting out some of the fat from the monthly budget, is another way to find money to save for college. Sallie Mae found three in 10 of those surveyed spend less on household and personal items, and use that savings for college.

Try tracking your spending for three months, and see if there's some money that can be redirected to a college savings plan. Budgeting can help too.

5. Have a plan

This is a big one from the Sallie Mae study: "Parents with a plan have double the savings." On average, parents with a plan had $22,169 saved for college, versus $9,208 saved up by those without a plan.

Having a plan means setting realistic goals: You could save for two years of private college and pay the rest out of cash flow, or try to save $50,000 by the time your child is ready for college. Specific goals like these are motivating, and help keep you focused on saving.

The numbers don't lie -- planners save more. Start by talking to your spouse or significant other and write down your goals for saving for college, making it a team effort. Take the time to check your progress too, and celebrate your successes -- perhaps reaching a benchmark like being halfway toward your savings goal, or having one year of college tuition saved. Make it fun. But most importantly, make a plan.

The five habits of highly effective savers

When it comes to planning for college, we can only control so much. We can't control the unseemly and unstoppable rise in tuition every year -- but we can control our habits. Routines like making regular and consistent contributions to a 529 college savings plan, or always using the cash back from rewards programs to save for tuition, can help. Earmarking the money from a side job to use for college, or spending less in general to save more for your child's education, will help too.

Above all, have a plan and get started now. They grow up fast, as the saying goes.