I'm the first one to admit that (up until a few months ago) I completely sucked at staying organised and being on top of things. Six months ago I was probably the last person to talk to when wanting organisational tips, but recently I've found a few things to organise a few of aspects of my life. Let's get straight into it :-)

Do it now; If possible, the easiest way to stay organised is to just do it at that very moment. Admit it, if you just do it when you think about something it's a lot more simple and you get a lot more done.
Write a list; maybe you're on the bus, walking home or just out somewhere where you can't do it at that moment. For me, the Notes app on my iPhone is a saviour!! I have lists upon lists of shit to get done and I try and do my best to do it as soon as I get home. If I am at home and am doing something else (like deciding that Netflix is more important than studying) I have a notebook in my bedside table that I write down my lists on.

Colour coordinate; all of my education things (notebook, folder, etc.) are pink, my history things are blue, communication is white and creative writing is black. That way, of a morning I know that if I have history at university that day I grab anything blue and go. It saves me time, and trust me that 2 minutes to get the right books is a lot of time when I always wake up late!!

Note cards; these come in handy for so many different things. Up until Grade 10 I was learning French and Italian at school and I would use one side for the French/Italian word and the other side for the English word. If I ever have way too much to do I will write one task on each card and stack them up in a prioritised scheme. This is where it will become how obvious of a nerd/dork I am (if this post hasn't done that enough already!), I have a cork board and sometimes I will arrange the cards (still in order of priority), annotate them, if it's for assignments I will also attach criteria, etc. Again, they are colour coordinated for each subject (yup, I had to order on eBay black note cards that I use a white pen on just because I had to have the colours match)...

Reward yourself; after I finish a section of reading, or a paragraph in an assignment I allow myself to have a couple of lollies or 10 minutes on my phone - sad, I know, but it works!