Forget design contests, they give you no real experience of working with clients, plus the vast majority of entries submitted are not original or clever, often infringe copyright, sometimes are exact copies and 99% of the time are complete shite. Plus, as Boss mentioned, you won't be getting paid for it, so why do it?
If you're going to work for free, ensure it's for a charity, non-profit organisation or local community group that could genuinely benefit from you, rather than someone who's looking to save money by using an exploitative service.
Read about good branding and identity design, understand what it is, what works, why it works, what doesn't, why it doesn't, and follow these simple steps:
- Sketch, sketch, sketch
Ensure the design works on paper before you move onto the computer
- Work in black and white until the design is finalised
If it doesn't work in black and white, it's not a good logo
- Design it using vector software
This will enable you to scale it up without losing quality
- KEEP IT SIMPLE!
The best logo designs are simple and clever. Gradients, glows and other bells and whistles just date and clutter a piece.
Designing a logo is hard, designing a good one is even harder, but like anything, practice and experience are the key, so keep at it.