Millennials are young, wild and free — but not for long.

Soon, they'll have to buckle down and prep for the day they retire. It might seem far away, but there are many strategic things they can do now to encourage a comfier future.

We spoke to Holly Perez, consumer money expert at Intuit and Mint.com, and Kali Hawlk, the finance and career blogger behind Common Sense Millennial. They shared their top tips for millennials looking to their future.

Above all, the top rule they all abide by is start now.

Student loan debt, credit card debt — whatever it is, tackle it head-on. Perez recommends aiming for high-interest debt first.

"Also, check whether refinancing your loans will give you a financial advantage," she tellsMash. "Any surplus of cash you get from these efforts, stash it away for retirement."

To learn more about refinancing loans, check out this piece from the Tuition blog, which lays out refinancing pros and cons.

If it's offered, take advantage of your workplace's retirement plans, be it a 401(k), 401(b) or Simple IRA, Hawlk says.

"That's free money on the table," she tells Mash. "Contribute enough to get the match at a minimum."

Reach out to your HR department or manager to learn how to capitalize on this opportunity. Ideally, you want to contribute 15% to 20% of your gross income, Hawlk recommends.

If you can't sign up for a 401(k) through your employer, consider signing up for a Solo 401(k) or SEP IRA, Hawlk says. Self-employed folks can still benefit from these plans, which are both tax-deferred.

One-participant plans, like a Solo 401(k), are treated the same way as employer-backed plans. For a complete breakdown of benefits, check out this handy guide from the IRS.

"Setting aside $4,000 per year starting in your twenties could make you a millionaire by 62," Perez tells Mash. That breaks down to about $333 a month.

A general financial rule of thumb is you need at least eight times your ending salary for your retirement. Break that up into incremental goals; for example, financial service company Fidelity suggests saving at least the equivalent to your current salary by age 35.

Sure, you're no Wall Street bigwig, but you can still get in the investing game.

"Here's my strategy: Buy low-cost, passively managed index funds and consistently contribute to my holdings no matter what the market is doing that particular day," Hawlk suggests. She recommends checking out Fidelity or Vanguard to explore investment options.

"Index funds are just a type of mutual fund," finance writer Matt Beck explains on his site. "And a mutual fund is simply a collection of investments (stocks, bonds, real estate, etc.) that you can buy as a package deal."

Becker's post explains index funds in detail, as does this post on Hawlk's blog.