It’s safe to say that guitar cleaning supplies aren’t exactly the “sexiest” guitar gear around. But if you play your instrument regulary chances are you build up sweat on the body’s finish and, perhaps more importantly, on the fingerboard. There are several must-have items that can help keep your guitar looking its finest.
At least once a week, you should give your guitar(s) a good polish (assuming you’ve played them). A good guitar polish isn’t very expensive (less than $10) and can help keep that “new guitar” look last just a bit long. You should always check to ensure that your finish is compatible with your chosen product though, as some vintage finishes can be a bit finicky. I personally recommend Dunlop and Dr. Duck products.
In addition to quality polishes, there are also waxes available that can help your instrument maintain its lustre even longer, though applying these waxes can take a bit more of your time. And again, always check to ensure that the wax won’t harm your guitar’s finish.
In addition to products like polish and wax that help maintain your guitar’s appearance, there are products that are specifically designed to help maintain and clean the guitar’s fretboard. There are even some products (like Fast Fret) that claim to improve your playing speed by lubricating the fretboard and neck. You need to read the instructions carefully, though, since some products don't work well with certain fingerboards. For example, you don't want to use lemon oil on maple fretboards, though it will work fine with ebony and rosewood.
Also, there are numerous cleaners that are intented to clean your strings and extend their tonality and life span. Fast Fret is also used by may players to clean their strings, though there are dedicated products for this job (including the really cool "String Cleaner" tool as well as Ernie Ball string wipes).
Finally, when you take the time to polish and clean your guitar, you may want to consider polishing the guitar's metal hardware. This is a personal preference, since many players prefer the look and feel of worn hardware. I'm one of them, though I've cleaned chrome and nickel hardware in the past with Blue Magic Liquid Metal Polish. Apply it with a toothbrush, and your guitar's hardware will start to shine in no time (just be careful when you apply it to pickups - use just a little bit so you don't get the clean inside the pickup).