Dont take offense but the question was a bit lame. Everyone is different and you do what is right for you. You will learn your own methods over the years to come and even if someone said that the way to do it was this way, it wouldnt maybe be the way you felt comfortable with.
But in answer to your original question.
I would offer the
tile up and make a few reference points on the
tile and guess teh shape. then i would cut it out without going up to the mark. The cut
tile would be offered up again to the obstacle and remarked and so on. I take little off at a time until its a nice fit. Rarely do i use a tape or ruler. I have a tape and ruler in my bag at all times but only used if needed. If i was cutting behind the toillet pan and i needed to know the width of a certain gap then i may use a slip of offcut
tile. Place that across the gap and mark it. Then transfer the mark to my
tile.
As for not being able to read the marks on your ruler, if you look around the tool shops or better still on the internet ( you can even buy left handed tape measures) you can find rulers with different markings on and some more heavier marked. If it was that bad then it wouldnt take you long to get a length of wood, mark it with a saw cut at regular intervals and paint the cuts with black to form your own ruler.