1. 1) Always design your logos in a vector application such as
Adobe Illustrator, and not a raster application such as
Photoshop, reason being the logo must be scalable without
losing quality and needs to appear crisp when printed on
anything from business cards to 20ft vinyl banners.
2) Ensure that the logo can be reproduced in a single colour,
such as black and still be recognisable. Think how the logo
will look on a press advert or fax letter, or reversed out of a
black background.
3) Bear in mind that the logo may need to be reproduced as
small as a postage stamp, so ensure that any fine lines or text
will still be legible when scaled down.
4) Limit your colour palette and specify your corporate colours
with Pantone or CMYK references to certify correct colour
reproduction when printed.
5) Finally bear in mind your use of typeface, colour and form
to give your logo the desired appearance of it's business.