The Control Panel
You have several choices here, you can use the original or build a new one from scratch. It all depends on what kind of controls you want, and how much money you have to spend. Building a new panel with a lot of controls can be very expensive.
There are many different things that you may want on your panel.
You will not be able to fit everything onto a single control panel. You are going to have to pick and choose what you want. If each player is going to have six buttons then you won't have room for a spinner, ecetera. There are a few issues that you should be aware of when selecting your controls. The first is that you are going to need a 4-Way joystick if you plan on playing Ms. Pac-Man, Donkey Kong, or any other game that used them. There is no way around that, those titles will not play correctly with an 8-Way stick, and don't believe anyone who tells you anything differently. The next thing you should be aware of is that you are not going to be able to reproduce the proper feel for all spinner games with a single spinner control, there were about a half a dozen different styles of spinners made over the years, and they all feel different. I prefer the Arkanoid style myself, but you might like the older Breakout style one a little better. The same goes for steering wheels, there were many types with many different feels, and many different modes of operation. I suggest skipping out on any sort of steering wheel, as MAME still doesn't properly handle them in most situations anyway.
My prefered layout is explained in the control panel node, but that may not suit your needs, or fit on your panel.
You should build a mock up of your panel and test it out using your computer. That way you can make sure that you managed to get the spacing on everything correctly. You may find that you play Ms. Pac-Man and other 4-Way games with your right hand, while playing 8-Way games with your left hand. This is common, and I suggest placing your 4-Way joystick somewhere near the center, so you can use either hand.
Once you have figured out your control panel. You will need a way to hook it up to computer. Your choices are keyboard hack (very common and very bad), Encoder (costs a little money but is very nice), or a Joystick hack (the easiest to do cheaply, but results vary). I only have one thing to say about this, buy an I-Pac encoder, it is all you will ever need. I have used all the other methods, and they all suck when compared to the I-Pac, buy the I-Pac and you will have no worries. If you really want to subject yourself to the torture of trying to hack up a keyboard or joystick then you can find complete instructions on all of them at www.arcadecontrols.com.