What defines a Muslim is his Faith; God is one & Prophet Muhammad (PBUH) is his last prophet.
There is more to being a Muslim then just avoiding liquor, Hindu clothes( as you mentioned).Though, these are considered as sinful acts but they don't set standards to incite dictum's whether a person is Muslim or not.
One of the fundamental beliefs of Islam are summed in the folllowing para
I believe in Allah (praise is due to Him alone), His angels, his books, his messengers (may they be blessed), the Last Day, Measurement (sometimes translated as pre-determination or destiny), both the good and the bad are from Allah the Exalted, and in life after death.