An important decision in writing your book is POV, or point of view. There’s first person (I), second person (you), and third person (he/she). To note, you really shouldn’t use second person. That’s only for those ‘choose the adventure’ books. Of course, you may be writing one of those, but generally speaking those are tough and definitely not one I’d recommend you try to write. If you’re good at it, chances are you don’t care what I have to say. But I’d strongly advise you stay away from second person. Those are just hard to write and hard to read.
Now that we’ve gotten that out of the way, the question of first person versus third person comes up. Perhaps you already lean naturally toward one of those. I’ve always been more third person myself, finding the first person stories I started containing too much of me (more on that in a minute). Some people are naturally better at third person, and some at first. However, if you’re a little on the fence, let me guide you.
The pros of first person are a more personal view into the main character’s thoughts and feelings. This can become a con, however, if your character become withdrawn, whether intentionally or on accident, or if you don’t want to reveal what’s going on inside them. It can further be a con as you can’t tell the reader anything the main character does not know. In the book I’m writing now, several times I go to the bad guy’s lair and describe conversations there that the main character has no way of knowing about. The book begins that way, actually. It’s useful to impart information the reader should know that the main character doesn’t. Further, I have found that when I write the main character under the term ‘me’ and ‘I’, I literally make them me. They’re no longer Bill (or whoever), they’re me. And I often take too much time to describe ‘my’ motives than necessary. In third person I let the actions speak for themselves. Also, it’s harder for me to write for a male main character if it’s supposed to be me. If these problems aren’t a problem for you, by all means, write first person. It can be quite successfully done.
The pros of the third person are that you can switch from character to character to the degree you wish, and peep into a random character’s feelings and thoughts, which can give the reader great insights. The cons are that you may not get personal enough with the main character. You may forget to tell the reader about their emotions or motives.
So there you have it. In the end it comes down to finding your own personal writing style. So go ahead and figure out your strengths and weaknesses when you write with either one.