There are certain things that you need to look when buying LCD Projectors.
1. Resolution – Make sure you get the required amount of resolution – higher resolution means more accuracy but more cost.
2. Brightness – If you use large screens then you need more brightness – about 2000 lumens is enough for normal use but in large halls you might need upto 3000 lumens.
3. Weight – there are more compact projectors available now – but they could be costly.
4. Contrast – choose a projector with a high contrast ratio.
Note: Make sure that the Lamp Life is at least 2000 hours because lcd projector bulbs can be pretty costly.
There are lots of other things that I might have left off. Please put a comment if I have missed something.