Volkswagen Repair: Starting problems with my 74 beetle, starter solenoid, battery clamps

Question
My 74 beetle will not start.  The starter, solenoid, battery and coil are all good.  The key switch when turned to the start position will not turn the engine over.  When this first started to happen, it would turn the engine over, but it wouldn't catch.  I have to assume that it is not getting spark?  Could the ignition switch be the problem?  Apparently the distributor has been modified also.  No points, electronic stuff in there.  I drove it to the store the other day, no problems, until I tried to leave the store (no start).  Any insight would be greatfully appreciated.

Answer
You are talking about two different symptoms here either your a)motor does not turn over      or  b)it turns over but does not start
If it is a) then the starter solenoid is at fault or the battery clamps need cleaning
  b)if it turns over, is there spark  Pull off a plug wire put in a plug and hold it 1/4" away from the block while some one else cranks it.  There should be a fat blue spark.  No spark?? does that apply to another wire?   How about the coil wire to the cap?   Are those little wires to the pos and negative terminals on the coil in good shape and not grounding out?  Yes?  Coil will be the suspect at this point.  If you had another coil to swap and try then do it(can come out of a Chev) to see .  Does that work Yes?  then coil is prob.  If not, then it may be in the distributor(I don't know how that works as I am a point man) but I would go there first.  Once that can be proven to work then we move back to the ignition.  Sorry, this a step by step process of elimination