(I'll get you - Leo Martin) Leo Martin describes in his book how he got criminals to trust him and work as informants for the german security agency.
p033 Find the positive in others. You are radiating the way you feel about the people you interact with. If you have negative thoughts about them you will nonverbally and unsconsciously display dismay to them.
p048 Look for commonalities and share personal information to build an
emotional connection. Source: Nachrichtenpsychologie 1
p050 share value and belief system, find or establish commonalities, share
personal information
p090 become interessting for the other person, so they initiate contact
p098 demonstrate high self value then share recognition
p105 change conversation topics frequently
p114 Leave the conversation on the high point. This way you have something to pick up on next time
p133 trust means keeping promises
p138 building insider jokes/rituals etc. create intimacy
p152 start with smalltalk (only 2-3 questions) then go to more personal topics
p158 Establish many events on many different locations. This creates the impression of a long time.
Use informal, personal language to create closeness (Du rather than Sie). If this is not accepted do it in your mind to adjust your language.
p201 People want to be understood. Understanding does not mean aggreeing. Find aspect that you can aggree to without problems.
p215 Create a positive atmosphere, ensure the other person laughed, smiled or chuggled with you before asking a favour