I've eaten on $2 a day and tried living on an $8.15-an-hour salary in New York City - here are my 10 best tips to save money

Use cash

When you have to stick to a tight budget, ditching your plastic cards for cash can make a world of difference. Simply withdraw a predetermined amount of money for the week and commit to spending just that amount (leave your credit cards at home if you'll be tempted to swipe them).

The cash-only diet forces you to stay at or below budget — once your wallet is empty, you're done spending for the week (or however long you planned your cash to last). It also gives you a better idea of exactly how much money you're spending and how much you have remaining in your budget. Plus, there's something about physically handing over bills — watching your money disappear right before your eyes — that causes you to value it more.

Track your expenses every day

I take five minutes at the end of each day to record everything I bought in an Excel spreadsheet. I've found that this habit is just as effective as it is effortless, for a few reasons:

1. It allows me to notice how easily expenses can add up. You don't quite realize how quickly you can blow through cash until you start writing down each purchase. The action of recording everything provides a new awareness that keeps me in check when shopping and has helped me become more deliberate with every purchase.

2. It holds me accountable. The last thing I want to do at the end of each day is have to record unnecessary or silly expenditures.

3. It challenges me to lower my costs each day, week, and month. Recording expenses becomes a game, and you start to see how many days in a row you can spend $0, or under $5.

Where you grocery shop (and what you buy) matters

Your grocery bill is entirely under your control — you're not locked into a contract like you are with your cell phone or internet — and chances are, you can find ways to cut back.

I stayed away from luxury or organic grocery stores and did all of my shopping at the famously affordable Trader Joe's. I also stuck with the basics, quite literally: During the Elon Musk Challenge, I purchased nine items, such as peanut butter, pasta, and oats.

The Elon Musk Challenge was extreme (and not entirely healthy), but it is possible to eat healthy on the cheap. You just have to know what to look for. Check out the healthiest foods at the grocery store for the least amount of money and 19 ways to eat healthy on a budget.

Go homemade

Like organic grocery stores, restaurants were completely out of the question during my month-long challenges. Restaurant bills and bar tabs add up quickly — one night out would have sent me way over budget. I also kept a healthy distance from drugstores, where it's painfully easy to spend $5 or $10 on a couple of Vitamin Wate's and snacks.

The more food you can make at home, the more you'll save. Plus, making your own meals tends to be healthier than eating out.

That being said, you don't have to completely deprive yourself of dining out — it's a fun way to socialize, and everyone is allowed the occasional splurge. Just make sure you allocate room in your budget before hitting up the restaurants and bars.

Plan ahead for unplanned expenses

One of the biggest take-aways from the minimum-wage challenge was that there are always unexpected costs — a birthday, a wedding, or a flight home, to name a few — and they can ruin your budget in an instant.

These unexpected costs aren't necessarily emergencies, and they aren't even always unexpected, but they aren't consistent, like rent or cable, and they can wreck your budget.

The best way to deal with them is to plan ahead as much as possible. It's impossible to plan everything to a tee, but you can look at each month from a big-picture standpoint, anticipate certain inconsistent costs, and set aside an appropriate chunk of money to accommodate those costs and keep your budget intact.

You don't have to say yes to everything

It is incredibly easy to spend money in any city — that's obvious. What became more obvious during both month-long challenges was how much pressure there is to spend. I found that it's straight-up awkward to show up at a restaurant or bar and sip on a glass of water while everyone else is ordering beer and appetizers. It was more awkward explaining why I wasn't participating: "I can't afford it."

It turns out that I'm not the only one who has felt awkward or embarrassed in this situation. As Veronica Dagher of The Wall Street Journal reported, "Many people would rather struggle to pay off a large credit-card bill than utter the phrase 'I can't afford it.'"

Peer pressure can easily persuade you to spend money that you don't have. For this reason I got comfortable politely declining most social gatherings. I did say yes to a few things, and it was equally valuable to learn that it's OK to show up, socialize, not spend any money, and focus on the company around you, rather than the consumables.

Walk or bike to work

I'm lucky enough to live within walking distance of my office, and it saves me around $100 on basic transportation every month. This may be more feasible for some than others, but if possible, trade in your car or public transportation for a bike — or your own two feet.

The cost of gas and car maintenance adds up — as do train and bus rides. Plus, you get the health benefits of an active commute, and don't have to deal with the stress of the road. After all, science says that commuting can have a severe, negative impact on your mental and physical health.

Find pleasure in things that don't cost much — or anything

I'm lucky enough to live in New York City, where there's an abundance of free things to do. I will note that it's much easier to head to happy hour after work or meet up with friends at a restaurant than it is to rally a group to go to a park or free museum. That said, after putting in the research to find a free New York activity and going out and actually doing it, it was 100% worth the time and effort. Just because wining and dining is the most popular way to socialize doesn't mean it's the only way to socialize.

The best savers simply choose to live modestly — they find, and enjoy, the wealth of cheap and free activities out there, such as cooking, hiking, reading, and taking advantage of the free activities offered by your city or town.

As Joe Udo, who saved over half his income and retired at age 38, writes on his blog, "Sure, it’s fun to spend money. I like eating out, traveling, and other entertainments as much as anyone. However, I think I found the secret to spending less money. You have to learn to enjoy free or cheap entertainments ... There are a ton of free things to do out there and you don't have to spend a lot of money to have fun."

Before making a purchase, think about what it could buy elsewhere

When living on an $8.15-an-hour salary, I started envisioning what the money spent on certain "wants" could buy me elsewhere. For instance, a $2 Vitamin Water is nearly equivalent to a subway ride — a few of those would end up getting me to the airport and back later that month for a flight out of LaGuardia.

This simple shift in mindset can be particularly powerful when you're saving for something specific.

For example, one couple who quit their jobs to travel the world used this strategy to save $8,000 in six months. They started envisioning what the money spent on each purchase at home would buy them abroad: "Say we wanted to go somewhere an hour away, which is about $20 in gas money," they told Business Insider. "That $20 is a night in a hostel, or the best pizza in the world sitting over the Arno River in Florence, or a full day's worth of food in Bali."

Focus on what you can control

Eating on $2 a day, or living on a near minimum wage salary, is far from glamorous — that part is obvious. Rather than focusing on the obvious, direct your energy towards problem solving and figuring out how to work with what you've got.

You have to mentally commit. Don't think, "Can I do this?" Think, "How exactly am I going to do this?"