It may seem like a small issue when you first start a poetry notebook, but the kind of notebook you get does matter. You'll be using the same notebook for a while, and you want to get one that will continue to fit your needs. For instance, if this notebook is going to be in a backpack or pocket, you will want to get one that will stand up to abuse. If privacy is a concern, get a notebook with a lock on it. If cost is an issue, stick with something like a school notebook. Other things to think about include what kind of lines, if any, you want on the pages in the notebook, what size notebook you want and whether you want a plain or decorated notebook.
Before you start writing, it can be useful to give your poetry notebook a focus. Decide what format and style you will write with, and stick to it as much as possible. You could only write a certain kind of poem in the book, or keep it free-form. You could do dated entries like a journal, work through the notebook pages sequentially or use pages at your whim. There are infinite options, and each notebook will be unique to your needs. Deciding on and sticking to a format can not only help your notebook to be more organized, it can also make it a more pleasurable experience to write in your notebook, making it more likely you will do so.
Possibly the most important aspect of the poetry notebook process is getting in the habit of using it. It's important to form a habit and stick to it, as not doing so often results in neglecting your notebook. If you are a structured person, pick a time of day or a day of the week to try and always work on your notebook. If you aren't able to do this, try and get in the habit of carrying your notebook with you throughout your day and writing in it when you have a free moment. Even small amounts of writing done on a consistent basis can add up to a quality notebook.
The writing contained within your notebook is of course the goal when using a poetry notebook, and there are a few good tools to use to get the creative juices flowing. Try taking your notebook to different settings -- such as a park, a busy street corner or your porch at home -- and write whatever comes to mind in that setting. Another good idea is to write to different kinds of music or sounds; even silence can produce some great work. You can also research different poetry types, such as the limerick or the haiku, and try to stay within their guidelines. Keeping yourself dynamic and trying different things will help your poetry and help foster your interest in writing.