As a Medic it is also essential to constantly be moving and check your behind once every 5-10 seconds. No one likes to get stabbed midway through charging or even at 100% charge waiting for the right moment. Don't be afraid to melee if the situation requires it as many Pyros don't expect it and you usually have enough health and time to put out the flames after the kill. If they airblast you away, whip out the needler and fire away.
Also get comfortable with using the Kritz on defense. Use it on certain classes depending on the situation; Soldiers for cramped places, Demos for people around a corner/pushing the cart, Heavy to scare people off and give your team room to breathe and build up. Just make sure they've got the right weapons you want first - no use kritzing a Demo with the Scottish Resistance. Sometimes a Kritz on offense is great for the same situations as well but I make sure that there is another Medic on the team with the Medigun running around because normal Ubers should take priority.
I haven't tried the Quick-Fix much because I haven't bothered to craft one so I'm not too sure what its pros and cons are.
P.S. Don't be like me and get too jaded if you stick to the guns and become a competent Medic. It is a great asset to pull out if you're going against stacked teams and you want to ruin their fun