Correct length of battery cables
 

I have older battery cables (one looks made up of heady duty electrical wire). I will buy new ones but wanted to know if there was a correct length and or routing that is 'correct' for our trucks.

I've learned that both cables are black, so I'll follow that. I did not know if the started cable from the positive was required to have a special routing?
Thanks

Jake- lacombe, la.