Step 1: Understanding the Concept: 
Effective purchasing involves making informed decisions to get the best value for money. This requires gathering information from various sources before making a purchase. 
Step 2: Detailed Explanation: 
- Advertisement: Advertisements provide information about a product's features, price, and availability, helping the consumer become aware of their options. 
- Personal experience: If a consumer has used a product or brand before, their own past experience is a powerful guide for future purchases. 
- Experience of other people: Reviews, testimonials, and word-of-mouth recommendations from friends, family, or online reviewers provide valuable insights into a product's quality and performance. 
Since all these sources contribute to a well-informed decision, they all help in effective purchasing. 
Step 3: Final Answer: 
A consumer can use advertisements, personal experience, and the experience of others to make effective purchasing decisions. Therefore, the correct option is 'All of these'.