1. Worst place to keep your toothbrush — the bathroom sink

There are 3.2 million microbes per square inch in the average toilet bowl, and all of those germs are propelled out every time you flush, settling on the floor and the sink. Keep your toothbrush behind closed doors in the medicine cabinet or a nearby cupboard.

2. Worst place to stash sneakers and flip-flops — the bedroom closet

Shoes track in allergens and contaminants. Leave your shoes by the front door.

3. Worst place to fall asleep — under piles of blankets

Being overheated can keep you from sleeping. Let your feet stick out from under your blankets.

4. Worst place to cool leftovers — in the refrigerator

Placing hot leftovers directly in the fridge can cause uneven cooling and possibly food poisoning. Leave food to cool on the counter for up to an hour after cooking, or divide it into smaller containers that can cool faster before refrigerating.

5. Worst place to sit on an airplane — the rear

The tail of the plane is where you'll get the bumpiest ride. Sit as close to the wing as you can.

6. Worst place to set your handbag — the kitchen counter

Tests have showed up to 10,000 bacteria per square inch on purse bottoms. Put your bag anywhere except where food is prepared or eaten.

7. Worst place to use a public bathroom — the stall in the middle

The center stall has more bacteria. Pick a stall all the way left or right.

8. Worst place to keep medicine — the medicine cabinet

The temperature in a bathroom can get well above the recommended storage temperatures for many common drugs. Keep medicine somewhere cool and dry, such as the pantry.

9. Worst place to use headphones — on an airplane, train, or subway

You're probably turning the volume up too high if you're listening to headphones in a noisy environment. Listen wherever you don't have to blast your music to enjoy it, or consider using noise-canceling headphones.

10. The worst place to pick up a prescription: the pharmacy drive-thru 

    In a survey of 429 pharmacists, respondents ranked drive-thru windows high among distracting factors that can lead to prescription processing delays and errors, says survey author Sheryl Szeinbach, PhD, professor of pharmacy practice and administration at Ohio State University. If you don't want to give up the convenience of a rolling pickup, be sure to check that both drug and dose are what the doctor ordered.

11. The worst place to stand during your first few fitness classes: front and center 

    You might think that you'd want to be near the mirrors so you can check your form, but your sweat session will be more motivating if your view is obstructed, suggests a 2003 study at McMasters University. In that research, 58 sedentary women all exercised at similar intensity levels. But those who did it in a mirrored room reported feeling more anxious about their body's imperfections after their workout than women who sweated without mirrors distracting them.

12. The worst place for a nighttime reading light: overhead 

    These fixtures put out relatively bright light — enough to significantly delay the body's secretion of melatonin, showed a 2000 study. That can wreck your night, since rising melatonin levels are a major cue for your body to prepare for sleep. A low-power light clipped to your novel will let you read but leave the room dark enough for your brain to transition into sleep mode. Try the LightWedge ($25 to $35; lightwedge.com) or the "Itty Bitty" Slim Book Light ($40; zelco.com).

13. The worst place for your coffee: the refrigerator or freezer 

    Think that you're preserving freshness by stashing it in the fridge? Think again. Every time you take it out of the fridge or freezer, you expose it to fluctuating temperatures, which produces condensation. "The moisture leeches out flavor — it's like brewing a cup of coffee each time," says John McGregor, PhD, a professor in the department of food science and human nutrition at Clemson University. The best spot to store beans or grounds: in an opaque, airtight container kept on the counter or in the pantry.

14. The worst place for your TV: wherever you dine 

    Studies show that distraction is your waistline's enemy — it can keep you from noticing how much you're eating. In a 2006 study, volunteers ate faster when watching TV than while listening to music — consuming 71 percent more macaroni and cheese when watching a show. If you have the tube on while cooking, turn it off before dinner at the kitchen table, and avoid being tempted into eating in front of the TV in the living room. The best place for your television: up or down a flight of stairs, so you have to "work" to get a snack — you'll be much less likely to munch.