can somebody give me guideline how to design good logo?
Simple is key! It has to mean something is another key.
I attempted to put a link to a really good article that would be a good resource here, but was blocked from doing so. That's too bad and would have been a nice assistance to the artist. :(
First and foremost - make sure it looks good in black/white/grayscale first before adding color. It's exceptionally important because not all applications of the logo will be in color. Additionally, attempt at all costs not to make it too busy - usually one or two elements is good enough.
//Jenn @ http://www.integraphix.com
First you need to know where your logo is going to be used. Is this for a brick and mortar company that will need to use the logo on print materials in many forms and media? Or is this strictly going to be used for someone's blog; never intending to be used on anything resembling a piece of paper? Or is this a brand logo, meant to be used for a specific product?
If if is the first, then reproducibility is the key. As Integraphix says, design from black and white up. Any corporate logo must be able to be reduced to its most simple form, black and white, or more specifically, all black or all white. Then design the color into the logo.
Think about what fonts portray that business. For example, if it's a construction business, you wouldn't use a script font; you would want a big bold thick font, maybe a sans serif or a slab serif. What about colors. Stick with solid colors and later work in gradients if you absolutely must, but I would stay away from them for a corporate logo.
Also look for multiple ways of designing the logo. Can it be used as a monogram (just the company's initials), would it work better as just being typeset, or maybe just an image; or some combo of text and images. It all depends on the company, the industry and the client.
If you are designing for a product, there is more flexibility allowed. Here it is more acceptable to use gradients, bevels, shadows and other effects not typically seen in a corporate logo.
For the Web, go nuts.
Each elemment must have a reason. You can try mixing ideas.
Your logo should be:
Effective without color
Your logo must be able to be scaled without losing its meaning