If you are not going to hire a designer here are some beginner tips: - choose at most 1 or 2 sizes (like 5pixels and 15pixels) - use only x*size for all yo

If you are not going to hire a designer here are some beginner tips: - choose at most 1 or 2 sizes (like 5pixels and 15pixels) - use only x*size for all your sizes (image sizes, margins, paddings) - choose only 2 or 3 colors (kuler.adobe.com). - check, double check and check again if what you created is easy to read/see. - check how your design looks in grayscale (will help the colorblind but is also a good contrast check) The limitations above will help a lot. But in the end it all comes down to experience and feedback from others.