This article was written by Amanda, a Colorado tech writer and an activist for children with congenital heart disease.

My conversion to frugality began about a year ago, but it's only been recently that I've become good at it. We've been saving money by being aggressive with a cash-only purchase plan. If we can't afford it, we don't buy it. This only works if you know ahead of time what you need and how much you're willing to spend on it.

One of my recent accomplishments was purchasing fall clothing for my children. I knew that they needed new clothes, and that the cost would exceed our discretionary spending. In our budget, we set aside savings for clothing. I had a budget of $125 for each of my two kids. Though they didn't need new clothes in August, I knew that was when I'd be able to find good sales and the best selection, so I planned ahead.

I researched online and found some things I liked. Then, I pulled everything out of my kids' closets. I figured out what fit and what didn't. I kept only items that worked with what they already had. Turns out my daughter needed lots of clothes but my son did not. Using some good coupons, I ordered everything I needed from Old Navy and The Children's Place online. Although this meant that I spent $10 of my budget on shipping, I know that:

• It prevented impulse shopping at the stores.
• I stuck with my plan because I could get everything that I needed without trying to find substitutes if they didn't have a color or item I needed in the stores.
• By Googling Children's Place, I found a 25% off coupon I could only use online, which was better than the 15% coupon they sent me.

I had plenty of my budget left over, so I got pajamas at the Carter's Outlet with a coupon they sent me, and got each kid four pair of warm PJs — all of which were necessary for the upcoming fall and winter. I got my daughter two pairs of shoes and three skirts at Target. I was planning on one skirt, but they cost less than one-third of what I had budgeted and I bought her lots of tights, so I knew we would use them (and we already have in the warm weather). At Target, the same Carters PJs were way more expensive than I had paid for them. My husband was impressed!

Of my $250 budget, I spent $230 including tax and shipping. My kids will be well-dressed until it gets hot again. I won't spend the other $20 — it just never came out of savings. The keys to my success were:

• Forming a plan and sticking to it
• Using time wisely
• Avoiding impulse spending
• Using good timing

It took me about six hours to look online, go through their closets, and order the clothes. It took another hour to go shopping. Those seven hours were well spent. I could have easily put $500 on my credit card in less than two hours if I hadn't thought things through. Essentially, I saved myself $35/hour by being diligent. By using the coupons I had (and finding better ones), I saved between 20%-25% on all of my purchases (except at Target).

My Target purchases were planned around back-to-school sales and end-of-season clearance. My daughter's skirts are actually summer clothes, but they're very simple and go well with the heavy tights I bought her and recycled from last year. Even though the two extra skirts I bought were semi-impulse, the shoes I bought on the same trip were $2 less than planned and the skirt was $6 less. That allowed me to spend exactly what I planned, and to get two items she could use. Now, if she couldn't have used them, then that would be wasteful.

This could have all backfired if I had gone shopping with my coupons not knowing what I was going to buy. I would have bought more and more just to save — same concept with clearance and back-to-school sales. The trick was to start with what I liked, and filter that through what we needed.

Also, I had to recognize that my daughter “needed” clothes; she's grown more than my son has, and boys' clothes are baggier and have longer wear-life for size if they don't get worn out. Had I spent only $125 on each, my son would have had lots of clothes he didn't need and my daughter would not have had enough. They're 3 and 4, so they don't know that I spent more on one than the other, and in the end it doesn't matter, because we were meeting needs.

Sales and coupons can either be a dangerous weapon of savings sabotage or a useful tool to maximize your money — the solution is to have a plan.

Amanda's previous articles at Get Rich Slowly include Use It or Lose It: Getting Value from the Things You Own and Baby Boom: The Shockwaves of a Lifestyle Change. Look for more from her in the future.