Shaykh Wasiullah Allahabadi (Allah have mercy on him) quotes from the book ‘Minhej al-A’amal’, that from the principles of the people of Tasawwuf are,
1. Eating the lawful (halal)
2. Having the beautiful manners (husun e khulq), and
3. Avoiding the company of those who do not share the same goal as the salik (azdad/najins).
Tasawwuf wa nisbet o ihsan, via Ma’arif e Sufiya, page 301-3