I know little of the critters you will be targeting...they all hang around water, well for the most part, and we don't have water. However, the closeness of set locations will be largey dependant on the population density of the critters in your area, the amount of time you have to trap, the terrain and the dispersal / activity pattern of the critters. Short of a book titled something like "The Art of Trapping", it would be hard to give you every situation in a single post. For example, if the critters you are after are highly localized, I'll guess beaver in dam situations, your traps maybe closer together within their rather restricted area or activity. You would, I guess target the big fellows and leave the kits for seed. Compare this to let's say Red Fox which, during dispersal move quite a bit and can travel long distances, you may have a pair of traps at good convergent point along the dispersal routes, with locations only every couple or three miles. In this later situation more traps closer together would not expidite your harvest...the targets are moving through rather than residing there as was the case with the beaver.
I'll let those that understand coon, mink, rats, beaver etc give you some more detailed guidance. My message is simple it all depends on what, where, how and why you are trapping.