Clean the battery, the battery compartment, the cables and their ends scrupulously clean. I MEAN CLEAN. Get out there with Fantastic and a toothbrush, if you have to.

Then, take some steel wool, or sandpaper, and scuff up the contact surfaces of the battery cable ends and the battery posts.

Then glop a whole bunch of grease (wheel bearing grease is the best 'cause it is the thickest and most temperature resistant and will stay where it is put compaired to other greases) on the post, before you put the cable on. Then put the cable on, tighten it up add evey more grease.

Make sure your battery is topped up with distilled water, to it's proper fill height.

Ocassionally, re-clean and re-grease the whole thing.

By the way, grease is okay between the cable end and the battery post. It will not hinder the electrical connection. If you look at just about every connector on just about every quality car made today, it is filled with silicon dielectric (that stands for insulating) grease. Good electrical connections are called "gas tight" connections because there is solid contact between the two metal services--a connection so tight that even a gas cannot pass. The grease will be displaced and, although you will not acheive a "gass tight" connection, you will achieve an excellent connection and the grease will protect the connection into the future.

Ken