1. Less is more.
If you make your logo overly complex you may think you have an original piece of art but people are bombarded by thousands of commercial messages per day. That overwhelming amount of information leaves little room to process complex logos. The fortune 500 spend millions of dollars researching consumer behavior. And if you look at most of their logos they're quite simple. Even the most complex one's like Starbucks have been updated to have a cleaner, more simple feel.
2. Make your logo readable.
Another thing you may want to consider is making the name of your company very readable in your logo. As your business grows it may not be important to associate your company name with your logo but in the early stages this can help. If you do include your name in your logo be sure to use a font that's generally bold in appearance and can be easily read. If you use an overly creative font it will be difficult for potential customers to read - especially at a distance.
3. Think about color.
Study after study shows that specific colors trigger specific psychological reactions. For example blue has been known to invoke feelings of confidence, trust, and loyalty where red invokes a feeling of alarm, aggression, and appetite. That is why you'll notice most fast food chains use dark orange and red color schemes. Other colors like green can represent calmness, environmentally friendly, or low fat. Think about the feeling you want to trigger in your potential audience when choosing the color of your logo. There is plenty of research available on the subject across the web. Take the time to investigate each color and choose the one that best fits your business.
Try to keep your logo to just one color. Keeping the logo to one color will provide an easy to remember, simple, and clean. In addition it will keep your printing costs down if you decide to make promotional items like t-shirts and mugs.
4. The technicals.
Once you've determined how you want your logo to look you'll need to actually create it. For this you will need an image editing software program. The best way to design a logo is to create a vector image. This is an image that can be made smaller or larger without losing image quality. Some software programs that allow you to create vector images are Illustrator, Photoshop, and Fireworks. If you're looking for a free option you might want to look at Inkscape.
When creating your file you may want to save it in several file formats. Although as long as you have the original, high quality vector you will be able to create whatever file format you need at a later date. The different file formats are for different types of use. If you're doing print advertising you may need the logo in something like EPS while on the web you may want the image to be a PNG or JPEG.