I removed the step regarding emulators and how I got the games for my Arcade Machines. If you need help with this, please search Google for other MAME instructions regarding emulators and such.
Step 1: Think to yourself...
How much money do I want to spend?
This is one of the most crucial questions you have to ask yourself before jumping in and start building an arcade machine. How much money do you have available to you? For me, I had to keep my budget down to about $200-$250 USD because I didn't have a lot of money. In fact, I had to pawn off some of my games and such just to get the funds to build this. I didn't have enough money for *actual* arcade controls because I spent most of the money in the wood, paint, and plexiglass, so I settled with two PS1 arcade sticks and a PS1-to-USB adapter. So, money is a big deal when it comes to this kind of stuff. If you have the money, go ahead and go all-out. If not, then just go with whatever works best for you.
Do I have the right tools for the job?
For a build like this, you'll need a couple of tools. Standard saws, drills, and other power tools will make the construction of an arcade machine run smoothly.
Do I have a blueprint of some sort?
Rome wasn't built in a day. But it was sure built off some sort of plan. So make sure you have a plan of some sort, which I will cover in the next step.
Will this be something I use often?
The thing about building entertainment machines or anything else of the sort is that they lose their shimmer after a certain amount of time. While you may build it and then play it every day for about a month, you might start to play it less and less often until it ends up in storage (like how my last build ended up). So, if you have a family (especially little kids), then it will be used often. If you live alone in your mother's basement at 23 years old, then you probably shouldn't consider doing this at all.
So, after spending a moment to ponder, let's get to building an arcade machine!