The four principles one should follow while accepting any achaaras : Aachaaras are meant for aayu arogya soukhyam (aachaarath labhathe hi aayu), sampath samruddhi ( aacharaath dhanam akshayam ) prosperity (Aachaaraath labhathey suprajaa) social bondage strengthening; Aacharaas are for building perfect personality (aacharo ahanthy alakshanam )
Sadaachaaraas are those which can bring permanent and sustainable beneifit for mind, body, family relation, cultural enrichment, social bondage and national integration (= sadaachaaraas). Those aacharaas which are irrelevant now a days are anaachaaraas; which create negatives for one or moe of the above six factors are duraachaaraas.
Four guiding messages for accepting an aachara as sadaachaara: Saastram Pramaanam = follow the scientific methodology for accepting an aachaara ; aapthavaakyam pramaanam = follow the opinion of the scholars in the subject ; prathyaksham pramaanam = seeing is believing follow what you could directly observe; anumaanam pramaanam = guess and estimate the observation you made before accepting anything.
Take one quarter of the knowledge from the teacher (aachaaryaath paadam aadhatthey) take one quarter from your own thinking (paadam sishya swamedhayaa) take the third quarter from the friends and colleagues through discussion (paadam sa brahma chaaribhya) Take the last quarter during the processing marching forward (sesham kaala kramena cha)
Achaarya is the person who has ound scientific knowledge on the subject ( aachinothi cha saastraarthaan ) who can teach in the simplest possible ways (sishyaan saadhayathe sudhee ) those who are practising which are preached (swayam aacharati chaiva) that person is the meantor / aachaarya )
Remember the teacher means guru; meantor means achaarya