Oh man, i can definitely say that i was an internet addict for many years up until very very very recently actually. It can't have done my education any good, but Alhumdullilah Allah made me do well in the end.
I don't know what advice to give you as nothing could stop me. My addiction has gone naturally and randomly and very suddenly, i think it is to do with other events in my life, but i think that is how changes happen in life. Other things takeover and shake up your world.
What do you do at the moment, study/work? How much free time do you have? Maybe you need to get busy with other things, which will leave less time for you to go online and also tire you out and make you forget about the urge to go on the internet. Once you go on it, you can stay on for hours, but if you don't get the opportunity to go on it then you are fine.
Practical tips i can give you, but i'm not sure if they'll be any use to you because i knew of them and never did them on purpose -
* if you have wireless connection and a laptop, then remove it. This way your laptop is stationed to only one place it can recieve internet, making you less comfortable and less able to go online all the time.
* carrying on from the first point, have your laptop/computer in another room, not your bedroom. And maybe in a place where you wouldn't naturally spend alot of time and would have to go to specially to use the internet. This will also cut off the ease and comfort of being online more frequently and for long periods of time.
* if possible, i don't know if it is, maybe have a internet time limit put on your connection, so it automatically cuts off after a certain time.
* tell someone who you may not be comfortable knowing how long you spend on the internet - the shame and the willingness to prove them you are better now can help your will power.
* lastly make dua - i made dua to improve my life, but never for my internet addiction to go down and i guess i should have, but Alhumdullilah Allah has helped me anyway.
Out of curiousity, what do you do on the internet? I used to go on a forum that wasted so much of my time, and the key was to stop posting there, i would still go on it to read but i stopped posting myself. This in turn removed the daily "ooh wonder what replies i've had, wonder what people have to say to my opinion etc etc" and this slowly but surely kills your need to go on that forum so much. I think that was the key to mine and a general disregard now to coming on the internet except for usefull things.