How to prepare for an ILR application?

I have been living in the UK for 1.5 hours as a dependant on my husband who is on the Tier 2 General Visa category.
I am working in the UK and have to travel outside the UK for business trips. I wanted to start gathering evidence now itself for travel history section in ILR, but I am not sure what are the evidences I need to start documenting?
Should I start saving my boarding pass? Should I save the immigration stamps? What does "a copy of a travel ticket showing the date of arrival" mean?
When does the "year" start? Is it 180 days every 1 year?
What the fields in the ILR form?
What other evidences i need to start saving?

Please help!

What date was your visa issued??

PBS Dependents do not require evidence of absence.