also if you speak to someone and they have a go at you, stand your ground and dont give in - youll get more respect rather than pussying out and letting the player win.
ive had many players ask me for higher wages - tell them to naff off because there is still time to run on their contract.
and if someone has terribly poor moral for a while warn them about transfer listing them if their attitude doesnt change, helps with discipline and it (normally) boosts their moral, very rarely will they be 'shocked by your threats', and even when they do stand your ground as i said previously.