for cranking prob, you prolly have one of two things..
1) corroded battery terminal.. check the terminals..and follow the wires also.. check where they connect to the chasis/starter/alternator.. make sure they're on tight, no corrosion.. the corossion would look like fuzzy white or blue fur.. its bad stuff, dont breathe it in.. take it off with bakingsoda/water mixture..dont get the baking soda in the battery or its gonna die.
OR its a bad starter. do the battery thing first, if same prob... its most likely your starter.