When thinking about buying your first home electronic keyboard, here are a few things you may wish to consider.

I would advise a keyboard with a minimum of 61 keys (preferably 76, or even 88, the same as a full size piano, if your budget can stretch to it.

61 keys is fine for a beginner, The cheaper 49 key instruments, are just too limiting in the range of music that can be played on them.

Make sure that the keyboard is what is called 'touch sensitve' ( sometimes called 'touch response') That is, the sound of the notes, is louder, or softer, depending on how hard the keys are struck.
Keyboards without this feature, are very boring, to both play, and listen to, as every note sounds at the same volume, and this does not allow for any expression to be used in your performance.
Generally, electronic keyboards do not have 'weighted' keys. The key action is similar to an elctronic organ, needing very little pressure to play, therefore, ideal for very young children, and adults with less mobility in their fingers.
Some instruments have built in lessons and teaching aids, such as keys that light up, to show which key to play next, when using the built in demo songs.
In my experience, this is a gimmick that soon becomes unused, but some people may find it useful. In fact, anything that can inspire a love of learning, and making music, should never be dismissed.

If you are mainly going to use the keyboard as a piano, be sure that the main piano sound, is of good quality, and one you would be quite happy to live with.
Most keyboards have a dedicated button, which immediately turns on the piano sound over the whole keyboard.

These keyboards can be immense fun to play, as they have a wide range of instrument sounds, drums, and even sound effects, such as birds chirping, applause, car sounds, and a host of others.

A good selection of backing and rhythm styles is provided, which can be used to accompany the right hand melody, using only a single finger to play the backing chords, making it possible to very quickly produce a 'professional' sounding performance. This can give young children, and adults alike, hours of fun, and really help to create the desire to learn.

Always listen to some of the built in 'demo' tunes, before deciding to purchase, as these will demonstrate the full range of sounds and capabilities of the instrument.

It is always worth a visit to manufacturers websites, as they often have online audio demos of their products, that you can listen to, to help you decide without the pressure of a shop salesperson hovering over you.
A few of the most common keyboard makes, are, Yamaha, Casio, Roland, and Korg, amongst others.

A facility to record your performance, is a useful feature. Even a basic on board two track recorder can be most useful, as well as fun.
You can always upgrade to a more fully featured keyboard, when you have reached the limits of your current one.

Most keyboards have MIDI or USB connections, for connecting to a computer to expand the capabilites of the instrument.
I gave a brief explanation of MIDI and how it can be used, on the Digital Piano Page

You will also find a headphone socket, for silent practice, without disturbing others, and one of the most underused features of most keyboards, is the 'Sustain' socket, usually on the rear,
This allows you to connect a sustain foot pedal to the instrument, similar to the right hand  pedal on a piano. When the foot pedal is depressed, the sound of the notes you are playing, will be held, before slowly dying away, giving you the ability to add much more expression to your playing.

A Guide to Portable Home Electronic Keyboards