Nemanja, this purely depends on the model you want to use. You want _inherit or _ineherits? Specify your question in a little detailed manner.

I know the difference between _inherit and _inherits, it's written in technical memento. I need help with understanding basics of writing new model or inheriting existing. Under basic I meen which methods I need to implement for my model. For example I have model people, and when my user click Save on adequate view I need to write data to few other tables, of course based on data that my user entered. How can I catch this event, and how can I achieve this?

_inherit seems right for you. Which methods to override depends on your need. create() for creatin new record, write() for updating data of record, unlink() when you remove that record! fields_view_get() when you want to alter the view archirecture dyamically!