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Getting the correct logo can be vital for your buisness and it's identity. For myself, the barcode logo was my original logo for poster design and flyer design but for CD/DVD & retail work i had to get a more corporate image. Also it was important to not have a barcode so to not cause problems with a sellable products actual barcode, so i came up with the "C" and "e". It works also as many companies have a standard circular logo.

For other companies and individuals, i try to get at much feedback before designing the logo itself, including:

What does your company sell?
A hi-tec logo for an antique shop wouldn't work right.
Do you want modern or classic?
What image and customer base do you target?
Colour or black & white?
Purely a personal choice.
Will it be used for large banners or only small scale?
That will affect the initial design for print quality. 
Simple or with effects/in 3d?
If you have a limited budget, one colour is cheaper to print.

The rest is spoken with the client to find out what image the company has so far and how they want to change, update or simplify.

Remember, every big selling brand, band or company has an instantly recognisable and defining logo so it can be very important.