1. Support Responsive Design
2. Be Built On New Technologies
3. Check For Live Theme Editor Tool
4. Own Perfect Interface For Your Store
5. Test Browser Compatibility
6. Be Optimized For SEO
7. Support Useful Module
8. Be Fully Social Network Integration
9. Possess User-friendly Interface
10. MultiLanguage And RTL Ready
VIEW DETAIL: http://www.venustheme.com/10-tips-to...magento-theme/