Zen Habit has an incredibly insightful post on how he got to 4,700 subscribers in just three months. He gives this advice:
1. Useful content, every day.
2. Conciseness and scannability.
3. Catchy headlines.
4. Listen to readers.
5. Respond to all emails.
6. Useful links.
7. Make lists.
8. Guest posting.
9. Always give tips.
10. Collaborate with other bloggers.
Excellent advice.