Beginner's approach to hacking the game

You want to hack the game or CREATE the hacks? The first is moron-proof, you just need RABCDAsm and a bit of brain. The second is "more complicate", mostly due to the fact you need to know something (AS3 I guess).

There are tutorials to be found here on clients and a few for proxys just takes a little digging around XD
or are you after something else?

What are you hoping to achieve / create?

Id assume someone with decent coding knowledge would atleast be able to use the search bar for a few seconds to see the hundreds of threads and tutorials that adress this. Read up, try things yourself or learn from the tuts, post when you have a prblem or issue with your project and people can help.
To start off, if.you want to directly alter the game you need to read write and edit as3, if you want something less direct, you could apply your java skills to modifying an already made proxy, or make your own.

Same as krazyshank
You can start by trying to update simple hacks like autonexus or numerical display.
I learned flash bytecode (this not really AS3 like this.

Are you trying to hack the game like get free items or get a hacked client