This is Tip #1 of the 30 Day Challenge to save $1,000.

The first tip is to go to the grocery store today and pack lunches for yourself all week. Sounds obvious, but below I'll include some specific tips and social-psychological techniques to make this actually work.

This tip reminds me of something I heard in college from a professor of mine, who made the point that lots of people look down on fields like communication and psychology because they seem self-evident. "Communication is measured by the usefulness of the theory, not the difficulty," she told me. It's easy to look down on tips like "pack your lunch" because it's so obvious, but it actually works.

How much you're currently spending

Let's look how much NOT packing a lunch is costing you. I'll assume you eat out 3 times per week for lunch.

Current lunch spending: (Eat out 3x/week) * (4 weeks in a month) * ($12 each lunch net with tax) = $144 per month on eating out

New spending to eat out: (Eat out 2x/week) * (4 weeks) * ($8 net with tax) = $64.

New spending to pack lunches: (Pack lunch once/week) * (4 weeks) * ($5 cost per packed lunch) = $20.

So $144 - $64 - $20 = $60 in savings.

Because you can break down the variables above (# of times you eat out vs. amount you spend on each lunch vs. cost of packing your own lunch), you can tweak each of them. For example, maybe you want to eat out 4 times per week but it will only cost you $2 each time. In that case, enjoy the week-old rotten vegetables you're buying. But if you tend to eat out at expensive restaurants with co-workers, maybe you limit it to once per week. Up to you.

Note that I didn't suggest going cold-turkey on eating out for lunch...because that will last about a week, then you'll give up. This is the key point I made in Set smaller goals: impress friends, get girls, lose weight. You can get better sustainable change if you slowly optimize, rather than quitting cold turkey.

Here's the concrete tip for today:

1. Decide how many lunches you're going to pack each week. More = save more money.

2. Go to the grocery store today.

3. Buy food for your lunches this week. If you want to shop for other stuff, that's fine, but the purpose of this trip is to get food for your lunches. If you accomplish just that, you accomplished your goal.

4. Let's say you decided to pack 3 lunches each week. Put 3 bags on your table and fill it with 3 bananas, 3 bags of chips, 3 whatever. This takes advantage of our laziness to pack lunch each day. Instead, by doing it this way, you batch the unpleasantness of preparing lunch. Now, each morning, just open up the fridge, take your bag, and you're done. (Bonus tip: To psychologically commit yourself to actually taking the bag, write "Monday," "Wednesday," and "Thursday" on the bag.)

5. For the days you decided to go to lunch, GO! This month, I want you to be strategic about eating out, so it's not just something you do because you forgot your lunch, shrugged your shoulders, and go drop $10 for your lack of planning. If you decide you're eating out on Tuesday and Friday, enjoy it -- you planned for it.

6. If a co-worker invites you to lunch, be prepared to say no. Try this: Thanks, I'd love to go, but I'm taking this 30-day challenge to save $1,000, so I'm not eating out as much. (This is related to inoculation theory in psychology.)

7. Be sure to read to the end of this post ("Last things to do"). Leave a comment describing how much you're saving with this tip.

Bonus reading about food and money

• Food and personal finance are similar. I highlight the similarities between money and eating, including how we know we should be doing better, feel guilty, etc.

• Food and personal finance are similar (part 2). More similarities: The role of experts in personal finance and nutrition.

• As a final note, I want to encourage you to be purposeful about eating. Next time you're at work and start munching on something (especially for people who have kitchens stocked with food), stop and think about it. Why are you eating? Are you bored? Nervous? Chances are you're not hungry. The best book in the world on the psychology of eating is Mindless Eating: Why We Eat More Than We Think.

Last thing to do

Leave a comment on this post describing how much you're saving with this tip. Each day, I'll ask you to post how much you've saved cumulatively. Use this as a way to track your own progress (it will also encourage others to join)

Sign up for more tips from Sethi's Web site

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