A good start would be 'how to develop a threat model'. There are very useful guide about it like the one written by EFF.
Security planning helps you to identify what could happen to the things you value and determine from whom you need to protect them. When building a security plan answer these five questions:
- What do I want to protect?
- Who do I want to protect it from?
- How bad are the consequences if I fail?
- How likely is it that I will need to protect it?
- How much trouble am I willing to go through to try to prevent potential consequences?