What are the rules for using 'will' for on-the-spot decisions, requests, and predictions?

Rules for using 'will':

• On-the-spot decisions: Used for spontaneous choices made at the moment of speaking. For example, if you're really tired, you might decide, 'I don't think I'll play football this afternoon.'
• Requests: Used to ask someone to do something. For example, 'Will you help me carry this box?'
• Predictions: Used for predictions based on what we think or imagine about the future. For example, 'Come hiking with me, Joe. It will be really nice!'

Note: 'will not' is contracted to 'won't'. 'Be going to' is used for plans.