Building and maintaining a lead database involves several steps: 1. Data Collection: Use lead generation techniques such as online forms, social media, and events to collect potential customer information. 2. Data Input: Manually input or automate the data entry process using CRM systems. 3. Data Validation: Regularly validate and update the data to ensure accuracy and relevance. 4. Segmentation: Segment leads based on various criteria like demographics, behavior, and lead source for targeted marketing. 5. Follow-up: Regularly follow up with leads through personalized communication to keep them engaged.