Two separate characters telling their story as first person.
Question: This is my first attempt at writing a book. I have planned to alternate my chapters with 2 main characters, both are equally important. I have started with the first character in first person. (her story is told in ch 1,3,5 etc). Now I need to fill ch 2,4,6 etc with the second main character's story, but I also want her to be first person. What tips could you give me so I may avoid coming across as an amateur/beginner. I am worried that I will use 'I/me" to much in the book, and that the reader will feel overwhelmed by having to 'live' both characters. The two stories and characters will meet at a point, and I will no longer alternate stories, and therefore continue with one POV, still in first person. Does this seem like a good idea as the reader or do I need a new strategy?
Nothing wrong with your strategy.
However, if you have two point-of-view characters, and use first person narration for both, the first important thing you should do is make it clear to the reader whenever you change points-of-view.
The best way to do this is to give each character her own voice -- her own distinct way of speaking which may depend on her age, culture, education, personality, etc. Don't make the characters too similar.
It also helps to include details at the start of each chapter that help orient the reader by making it clear that a different character is speaking.
The second thing you should know is that every POV character is the hero of her own story. It helps if that story is a complete arc. In other words, even after the two characters meet and the one character takes over from then on, the reader may want to know how the other character's story ends. How does she resolve her inner conflict? Does she end up in a better/worse place? You may want a chapter at the end in that character's POV to tie up loose ends, or find a different way to accomplish this.
Don't worry about writing "I" or "me" too often. There are some words and phrases you will write thousands of times (e.g. "he said"), but they don't bother readers. In fact, they are almost invisible to the reader, even if they are boring for the writer.
Best of luck.