How does one make a good tester ?

For starters, formal training and gaining experience in both:
1. Manual testing, and
2. Quality Assurance

Technical:
1. Understanding of systems and software
2. Programming skills are helpful

Skills a good SQA person has to have:
- 'test to break' attitude,
- Ability to take the point of view of the customer,
- Strong desire for quality,
- Attention to detail.
- Tact and diplomacy are useful in maintaining a cooperative relationship with developers,
- Ability to communicate with both technical (developers) and non-technical (customers, management) people
- Previous software development experience can be helpful as it provides a deeper understanding of the software development process, gives the tester an appreciation for the developers' point of view, and reduce the learning curve in automated test tool programming.
- Judgement skills are needed to assess high-risk areas of an application on which to focus testing efforts when time is limited.
- You must be able to understand the entire software development process and how it can fit into the business approach and goals of the organization.
- Ability to understand various sides of issues
- Patience
- Ability to find problems as well as to see 'what's missing' is important for inspections and reviews.
- Tenacity
- Resourcefulness
- Team spirit
- Salesmanship
- Ability to learn quickly
- Ability to research
- Perseverance