Does it matter how each line is indented? Can all the lines be right under one another or do I need to press 'tab' to make an indentation for some of the lines?
You can decide how you want to indent, but i would do something practical, code of more then 50 lines which is not indent, is a disaster (trust me, you easily pass the 50 lines most of the time), even less then 50 lines it isn't nice to have non indented code
How much you indent, or if you indent at all, is completely optional and based on personal preference. I always indent for each line because it helps me figure out where things go, but if you don't like to do that, then you don't have to.