Key features you will see quoted along with projector makes and models relate to
BRIGHTNESS - Quoted in ANSI LUMENS. Typical desktop units will be aorund 2500 lumens.
RESOLUTION - Relates to the number of pixels used to create an image. The standard for business projectors is still XGA (1024 x 768 pixels), although widescreen resolution are increasingly common.
TECHNOLOGY - Most commonly used in business projectors is LCD (Liquid Crystal Display). Other types are DLP (Digital Light Processing), often used in home cinema settings, and LCOS (Liquid Crystal on Silicon). LCOS currently offers the best image quality but there is a corresponding price tag.
HOW TO SETUP YOUR PROJECTOR
Standard projectors are generally fitted with lenses that operate at around a 2 to 1 ratio. In laymans terms this means that to fill a 1.5 metre wide screen you would need to be 3 metres back. To ensure a rectangular image most projectors will require that the lens is placed level with the bottom of the screen (ie not projecting upwards or downwards), and at right angles to the mid point of the screen. Image size can be adjusted using zoom, and keystone if required.
CONNECTING YOUR PROJECTOR TO A LAPTOP
Typically still done using a 15-PIN D-SUB connector, although some laptops may use HDMI connectors. Macs are supplied with various outputs which require conversion. MDP (Mini Display Port), Thunderbolt, mini HDMI and others. It's generally advisable to connect the computer to the projector pior to turning anything on, and then fire up your projector. Once the projector is warmed up and working then boot the attached computer - in most cases it will detect the attached projector and enable the external video connection.
DO'S AND DON'TS
Never turn off the mains power to your projector whilst it is running - Lamps are fragile and expensive and must be cooled fully prior to turing off your projector. Do turn your projector off by pressing the on / off button on your remote (or on the projector, but NOT the one next to the power input).