One of the best ways to discover the Riesling styles you prefer is by doing a side-by-side tasting of a range of styles.  Ask winery staff, wine retailers, or a wine loving friend for guidance.  Or research the web and read recent wine aricles or blog posts.  Most bottles include the RS level on the back label.  Also consider wheter you'll be drinking the wine as an aperitif or with food. 

• Dry-below- 9g/L RS (Residual Sugar)
• Medium Sweet- 9-50 g/L RS
• Sweet- 50-100 g/L RS
• Dessert Style- Above 120 g/L RS