I saw TF2 and Smiled.

Yeah as a Spy its a game of psychology. One trick I use is when trying to get into their base, go invisible during crowded areas make sure you uncloak in privacy (Its easy to hear the uncloack with headsets) and if trying to get into the enemy base retreat byw alking backwards towards it, looks more like you're going to retreat to get ammo/HP
Also, make sure you're facing your team msot of the time, looks more liek your trying to target the enemy.
Another good trick is if they suspect you're a spy and shoot you, dont run, continue walking in the direction you were or turn and look at the shooter and hope they stop. And other than that just try not to draw attention to yourself.
Also make sure you communicate, as a Spy you can provide a great distraction by sapping sentries and running to draw enemy fire as your team makes a push.

i usually target my team and sorta strafe while looking for an easy target.

doesnt usually work though... maybe it's cos im a medic?

Oh, disguising as a Medic is always a bad idea, Especially on the console versions as you dont have an Uber charge. If you manage to kill someone on a server with respawn time, try to disguise as them.
As a spy you should plan ahead and just try to manipulate them.