Technology: i’d go for an LCD technology because of its maturity. DLP is also interesting to look at, but the newer LCOS, promises a disappointingly short lamp life for now.
Brightness(lumen): The absolute brightness of the image. Anything less than 3000 lumen is not worth considering these days. Allows you to see something even if the room is not completely dark.
Contrast ratio: the difference between black and white. same as LCDs. more is better. try 400:1 or better.
Aspect ratio: is directly linked to the display resolution. 16:9 is standard widescreen, 16:10 is computer widescreen. 4:3 is standard photo and TV aspect ratio. older computer screens also used this. Aspect ratio must be switchable.
Resolution: bigger is better. cool to have full HD 1920×1080 (16:9) or even 1920×1200 (16:10), but expensive
Fan noise: expressed in decibel (dB). dB are logarithmic, at every 6dB the sound is twice as loud as the previous. 40dB is certainly unbearable for a home cinema. http://www.loveprojector.com/
especially check for lamp failure policy, dead pixels, factory damage replacement policy.
VGA/D-sub15 – analogue connector. must have for work. older equipment usually have this, most non-fruit laptops. you can sometimes buy an adapter.
composite: analogue, in use with older smart phones, video cameras. Obsolete, but still prevalent
S-video: analogue, better than composite, multi-channel cable, but was designed with relatively short cable lengths in mind. may be more sensitive to noise. Uncommon today.
SCART: colossal analogue connector with big wires. An old fashioned CRT set is highly likely to come with one of these. Also obsolete.
DVI- (variations I and D, D is better) standard digital connector slowly falling out of favour due to its huge size. Not found on most laptops
HDMI – high definition digital connector, standard also supports audio
DisplayPort – faster than the previous two. 2014 slim laptops tend to come with miniDisplayPort, made popular by Apple. a cheap cable ought to do it without conversion loss.
memory cards, PCMCIA, wi-fi – may allow operation and control independent of a PC