Product manuals for appliances and other major household devices are a bit like martini glasses. You never use them, but the minute you get rid of them, you realize you need them.

Although some people choose to dispose of the hard copies and find their manuals online when necessary, it's wise to keep some record when you buy an air conditioner, refrigerator or stove. Whether you prefer to keep them online or have hard copies, here are ways to keep appliance manuals organized.

What to keep, what to toss

Let's be reasonable. It's not necessary to keep the paperwork that comes with a product such as a fan, hair dryer or coffee pot. If the item has an on/off switch and you know how it works, feel free to toss the paperwork.

Manuals and warranties for bigger (and more complex) appliances such as your dishwasher, dryer, air conditioner and water heater can be stored in labeled files and organized by category. Categories might include "Technology," "Kitchen," "HVAC," "Outdoor" and "Miscellaneous small appliances."

Use category names that make sense to you, and keep your files current by throwing away old documents when an appliance is replaced.

If you are on the fence about items that fall in between, say, a fan and a major appliance, think about how often you might need the manual. For instance, you might want to keep a bike manual for occasional reference. It also may make sense to keep the manual for a kitchen appliance that you use only once or twice a year.

And there are some items for which you'll want to keep the manual for as long as you have the item, such as a crib or car seat. Some baby and toddler items have important height, weight or age recommendations, and if you eventually give those items away, it's best to also pass along the paperwork. If you might someday sell an item, all the more reason to keep the manual.

How to organize hard copies

Before tossing a jumble of information into a file, sort through the paperwork that comes with your purchase. Keep the manual and warranty, and recycle the rest. Also, write the purchase date and vendor on the front of the manual before filing it.

The files will be bulky, and you're not going to access them frequently, so they don't need to be stored with your other household files. Instead, keep them in a secondary filing cabinet or in a clearly labeled box on a shelf in a closet or in the basement.

Regardless of how you choose to organize your information, just taking the time to do it will prove useful not only when repairs are needed but also if you sell your home.

Ways to store electronically

It's true that most of us will rarely, if ever, look at the manual for things such as our washer and dryer or water heater, which is why some people toss that paperwork. But you need to record model numbers, serial numbers and dates of purchase electronically, and use online product manuals to find the pertinent information when necessary.

The key to making this work is to accurately and consistently record the relevant information. Some people will create a simple document or spreadsheet, while others prefer using a digital tool such as Evernote, in which they can type the essential information or upload photos of box labels or the front of the product manual. As with any organizing task, pick one option and stick with it.

Before you recycle the hard copy of a manual, search for your specific model's manual to make sure you can find it online.

Whether you decide to keep manuals as hard copies or electronic ones, having a system in place will prove invaluable the next time a random battery needs changing or an appliance inexplicably starts beeping.