(I will not be held responsible if you jack your stuff up...)
Now that is out of the way, let's get down to business!
I love gaming, plain and simple. But there's a special place in my heart for the classics like Sega Mastersystem, NES, SNES, Genesis, 3DO, etc.. but most of my collection was sold off years go. Now that I'm an "adult" I can do what I want, and that includes capturing a piece of my childhood. But after 20+ years, that childhood can become dirty and beat up. What do you do?!
Clean it up of course!
With just a little patience (and 90+% ISO, glass cleaner, and a magic eraser) It's very easy to clean up dirty nes, snes, genesis, n64, and whatever other cartridges your system of choice is.
Use magic eraser on the case, but be very careful not to hit the labels or any other stickers as it WILL cause damage. Glass cleaner on a microfiber cloth is great for cleaning the delicate parts like labels, and ISO to clean down the pins on the board, and any other stubborn stains. Use cotton swabs on the hard to reach areas with glass cleaner, and on the pins with ISO.
I've picked up many games, systems, etc that look nasty, but after a little bit of TLC, and taking my time, I have items in my collection that I'm more than proud of (plus it can increase value if done correctly).
(This isn't a how-to. I'm not going to offer support on how to do it, or offer any types of warranties if you jack your stuff up. Stuff like this takes experience, so, to quote "Jackass" do not attempt this at home)