How many handsets will you need? If you need more than one handset, it's almost always less expensive to buy the extra handsets as a part of a cordless phone package. Many models can support additional handsets as well, but buying those separately can get expensive.
What features do you need? Cordless phones can vary quite drastically by their feature sets. The most robust models will link to your cell phone via Bluetooth, which lets you place and receive calls via your mobile phone line from any of your cordless system's handsets. Other popular pluses include talking caller ID, call screening, and call blocking. Not everyone will care for these bells and whistles, however. At the very least, consider a cordless phone with a 50-number phone book (or larger), speakerphone and voice-mail indicator. Backlit keypads as well as conferencing and intercom features are also appreciated by users.
Do you need an answering machine? Some of the best -- and priciest -- cordless phone models now include a built-in digital answering system. Most are fully featured, with things like the ability to record a greeting using a handset, audible message alerts and adequate recording time (15 minutes or more).
Don't forget message quality. If you opt for a cordless phone with an answering machine, don't assume that just because it offers crisp, clear sound during phone calls that it will sound great when listening to messages it records. If you expect to rely heavily on a cordless phone's answering-machine feature, be sure to consider message quality in your buying decision.
Do you need two phone lines? Some cordless phones support up to two phone lines. Some models offer distinctive ringtones for each line and support three-way conferencing between both lines and a third party.
Does anyone in your family have special needs? Many modern cell phones are hearing aid compatible, but some go further by providing features such as extra-large buttons, easy to read displays, talking caller ID, and sound amplification.