Starting the birthday book brought trial and errors. Things that seemed to be mistakes turned out to be very accurate. Those “mistakes” show the road my book has gone down to become what it is today. But if I could fix them, this is one thing I would do.
A “mistake” made in the beginning was not always using the right pen.
Now, what is the right pen? What it would be for me, may be something different for you. You may want everyone to write with whatever they want to write with, to show how different people are. Maybe you want to use a lot of different colors. Maybe you want girls to sign with pink and boys with blue….who knows what is right for you?
What I found to be right for me is the pen my daughter gave me with my book. It is perfect because it writes clearly, cleanly and easily. Not like this! 
No blotches and no bleeding go through to the other page. If this is what bled through, think how overpowering it is on the other side of the page. And what happens to the person I find who has a July 15 birthday? Only time will tell.
And as seen in this photo, one signature overpowers the entire page. So that is when I decided to carefully provide the pen that works best for my book.
So pick your weapon, keep it on hand and find your right to write!