The "Bullet Journal" method of organization, designed by Ryder Carroll, is made to be simple and task-focused: all you need is a notebook and a pen. If you have found planners with prescribed sections and space to be too confining for your purposes, the Bullet Journal means of creating your own planner can be the solution. Design as you go: if the spread you use one week doesn’t work, fix it for next week.
Bullet Journaling gives you the framework; you fill in the rest!
X Task completed
> Task migrated. Every week/month, look back on what you didn't accomplish the previous week/month and migrate the tasks to the new time frame. Don't migrate a task if it's not worth your time!
< Task scheduled
- Note bullet
* Priority signifier
! Inspiration signifier
and more as you need/think of them:
Put the key to your bullets somewhere near the front (after your name but before the Index, maybe).
PAPER: There is no official journal/notebook that you must use in order to have a bullet journal. You can use whatever works for you. That said, there are benefits to using a graph-ruled or dot-grid-ruled notebook, given that you will be establishing your own layout and designing works easier when you have something to go by.
SIZE: Again, up to you. A5-sized notebooks (approximately 8.3" x 5.8") are popular because they have enough space for a layout without taking up too much room in backpacks/purses/whatever.
BRAND: Popular brands are the Leuchtturm 1917 and Moleskines. Pay attention to paper density (usually some number marked in GSM, Grams per Square Meter, like 80 gsm), which indicates whether ink will bleed through. But if you don't intend on doing much that might bleed through, this is less of a concern.
PENS: Any decent fine-point pen will look lovely on your page. If you like color, Sharpie pens are always just right.
OTHER: Washi tape, stickers, stamps... whatever you like to look at.