Check couple of journals:
You should do some research before making your own journal. Find out a person who makes a nature journal and ask him/her to show their work to you. This will help you understand the basic technique of compilation.
The type of journal:
First and foremost thing you will do is to decide the type of journal you want to compile. You can make a journal that only covers birds and insects. There are also journals that comprise of an overview of nature. In this type of journal, you record whatever you observe and feel. Similarly, you can also make a journal based on a particular trip. Things will become lot easier if you are focused.
Get a suitable journal:
Your next step will be to get a suitable journal. You can purchase it from any good bookstore but if you want to be more creative then you can make your own journal. However, do not neglect the importance of the quality of the paper. Your journal should have A grade paper and a high quality cover. The size of journal depends on the size of drawings so keep this factor in mind while purchasing or making a journal.
Assemble everything in a bag:
Now you need a bag to keep your journal and other equipment safe and secure. Get a camera, sketch pencils, brush and water paints. Decide a location and start observing things around you. Spare some time for this activity everyday and you will see how well you are doing.
Record your observation on the spot:
While observing things, keep taking notes and record your feelings and observations without any delay. Sometimes, relying on a memory can damage the credibility of your nature journal.