Cable Notes:  This is based on Stompin-Ground's experience, observation and testing of many cable over the years.  Your results may vary.  Cables have a lot of mysticism, voodoo and hype surrounding them.  Let's try to get real here.

Capacitance is probably the most influential factor on the sound of an instrument cable.  This is particularly true for passive, non-buffered, guitar signals.  Active or buffered signals are influenced by capacitance to a lessor degree.  You can also have much longer cable runs in a buffered system whereas you probably will want to keep cable lengths down in a non-buffered system. 

Resistance has less influence for instrument cables due to an instrument's very low voltage and amperage.  It is a greater factor when selecting a speaker cable as the current requirements are much higher.

Wire Size (AWG):  The smaller the AWG number is, the larger the diameter of the conductor.   It's not such a factor on sound but more for physical strength.  An AWG of greater than 24 may not be suitable for a long lasting cable that gets plugged into your guitar and gets pulled and abused more than other cables.  An 18 AWG size is very strong.  You might note however that the capacitance is usually higher for larger cables and lower for small AWG sizes.  Pedalboard cables, back line cables and other patch cables are typically fine using smaller 20-24 AWG sizes that also yield a lower capacitance.  Your main cable that plugs into your instrument may benefit from a larger 18-22 AWG size for it's strength.

Oxygen Free Copper (OFC): High purity copper used for instrument cables to further reduce coloration.  There is a little hype here as most copper used for electronics are pretty pure and the tolerance differences between them may not be significant according to many engineers.

More to come...