When i use an external cooling fan (electronics) where is it best to point fan?

Well, Considering that server rooms have AC running through the floor to cool their machines and server stacks, I would say the best place to blow cool air into your electronics would be from the bottom of the machine. If this is the kind of thing you are looking into and it sounds feasable, lift the electonic equipment off the floor and put a fan under it. Of course, your question is quite broad, what kind of electronics are they? The small electronic alternative would be to blow the air into a part of the machine that is not blowing air out, where the machine is sucking air in.