Ease of Use. Make sure you understand how the instrument's controls work — additional features are of little use if you can't figure out how to use them. Ask to see the owner's manual (or download it from the manufacturer's website) and make sure that it's understandable.
Cabinet Type. Another factor that may shape your options is where the instrument will live. Is space at a premium? Are there limited placement options? If home is a dorm room or a small studio apartment and you need to make the most efficient use of every square inch, you may opt for a portable model (not a furniture-style cabinet) that can be placed on a stand for practice and stuck in a closet when not in use. Bear in mind that this type of design, typically called a slab, doesn't necessarily limit the quality of instruments available to you — professional stage pianos also fit into this category. Slabs generally come with a single pedal, but many have optional stands that, like an acoustic piano, have three pedals. If you do go with a stand, don't get the cheapest one you can find. These are fine for 61-note portable keyboards, but tend to wobble when supporting the greater weight of a digital piano, and may not be able to be adjusted low enough to put the keyboard at the proper height from the floor (about 29 inches to the tops of the white keys). It should be noted that portability is a relative term: instruments in this category can range in weight from 25 to over 70 pounds, without stand.
Another option in the entry-level category is what is variously referred to as the vertical, upright, or console digital piano. The cabinetry of these models ranges from two flat side supports with a cross member for stability, to elegant designs that would look at home in the most posh surroundings. It's common for individual models in this category to be available in multiple finish options, including synthetic wood grain, real-wood veneers, and, on some of the better models, the lustrous polished ebony often found on acoustic pianos. Most of these models have three pedals.
If space is no problem and you love the look of a grand piano, several digital pianos are available in "baby grand" cases. Remember that, most of the time, you pay a significant premium for this look, and that few of the digital grand models actually use the additional internal space to enhance the instrument beyond the non-grand model it's based on. There are two size classes of digital grands, one about five feet long and the other closer to three feet — just long enough for the tail to curve in a quasi-grand shape.