Craftsman snow blower, model #536884822 will not start. First time in 12 years. Have replaced spark plug, gas, used fuel start spary on carb and still no start. Help!

When troubleshooting small engines, you need to ascertain 3 things:
a) Air - ignore, because no air cleaner
b) Spark - take spark plug out and hold firmly with something insulated and try to start looking for a nice blue spark
c) Fuel - Spark plug should be wet if it didn't start. Try fuel in carb. Carb cleaner is better. Do not use starting fluid. You can have too little or too much.

Check for spark first and report findings.

Thank you keep it simple... I replaced the spark plug again, got it wet, added some starter spray to the carb and it started after about 10 pulls and 2 primes. However, I need to keep the choke about 1/2 way during continued use otherwise the engine dies.

Use mid grade fuel at the very minimum.

Considering you have plug problems, it's probably time to remove, disassemble and clean the carb thouroughly and re-adjust.

Probable cause: Gas left in tank/carb for an extended period (over 3 months without fuel stabilizer like Stabil). Don't overfill the oil.

When you pull a plug and test start you need to ground the plug to the engine to get spark. If you just hold it in an insulated glove or rag there will be no spark. If it keeps needing 1/2 choke after many minutes of running you may need to make the mixture richer by backing out the "rich/lean" screw a half turn.

Sounds as though you have carb problems. Clean and readjust the carb.