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