Caring for a String of Watermelon (Curio herreanus, formerly known as Senecio herreanus), known for its beautiful bead-like foliage that resembles tiny watermelons, involves providing the right conditions. Here’s a simple, numbered guide for its care:

1. Light Requirements: 
   - Bright, Indirect Light: Prefers bright, indirect light. Some direct morning or late afternoon sun is beneficial, but avoid intense midday sun to prevent leaf scorch.
   - Indoor Light**: Place near a sunny window with filtered light.

2. Watering:
   - Moderate Watering:  Allow the soil to dry out between waterings to prevent root rot.
   - Reduce in Winter: Water less frequently during the winter months when the plant's growth slows down.

3. Humidity:
   - Low to Moderate Humidity: Prefers average indoor humidity levels. Tolerates dry air well.

4. Temperature:
   - Warm Temperatures: Thrives in temperatures between 65-75°F (18-24°C). Protect from cold drafts and avoid temperatures below 50°F (10°C).

5. Soil:
   - Well-Draining Mix: Use a well-draining cactus or succulent potting mix. You can amend regular potting soil with perlite, coarse sand, or pumice for better drainage.

6. Fertilizing:
   - Minimal Feeding: Fertilize sparingly. Use a balanced, diluted liquid fertilizer once a month during the growing season (spring and summer).
   - No Fertilizing in Winter: Avoid fertilizing during fall and winter when the plant is dormant.

7. Pruning:
   - Occasional Pruning: Trim back leggy growth to maintain a bushy appearance and encourage new growth. Remove any dead or damaged stems.

8. Propagation:
   - Easy Propagation: Propagate by stem cuttings. Allow the cut ends to callous for a day or two before placing them in well-draining soil. They can also root easily in water.

9. Support:
   - Trailing Plant: String of Watermelon is best displayed in hanging baskets or pots where it can trail down. Ensure it has enough space to cascade.

10. Pest Management:
    - Monitor for Pests: Watch for common pests like mealybugs, aphids, and spider mites. Treat infestations promptly with insecticidal soap or neem oil.

By following these care instructions, you can keep your String of Watermelon healthy and vibrant, enjoying its unique and attractive bead-like foliage in your indoor or outdoor space.