batcakes
The key to bullet journal is having a space - probably 3 pages or so - at the front, where, as, you fill in the journal, you create the contents page. It's such a simple thing but makes life so much easier. You can put wished you like in your journal and it's still quick to find it again.
Common things to include:
A monthly calendar
A future log in which to list events not covered in the monthly calendar
A weekly diary / to do list.
You can add whatever you like.
If you have a pen and a notebook, you can bullet journal. A lot of bujo wankers favour the Leuchtturm 1917 dot grid a5 book, but there are plenty of inferior cheaper alternatives.
There is loads of information about bullet journalling online for free. Google Ryder Carroll, the grandaddy of the bullet journal.
The name 'bullet journal' comes from Carroll's system of different bullet points to help clarify information on his own journal, but the joy of bullet journalling is the flexibility. I cba with fancy bullet points, so I don't use them.
Lots of people get very creative and elaborate with the presentation of their bullet journal. If you have the time/inclination, you will find a lot of inspiration on Pinterest etc