You always want someone watching the flank, whether it be a roamer in 6s (soldier that roams and tries to get important picks), a scout, a heavy, or a pyro. In competitive, medics are usually guarded, and have lots of comms (information) delivered to them. You always want to have eyes on the main passage, the flank, and behind you. + Another point is to watch out for the enemy team. By keeping your team alive, you basically are doing damage by keeping them alive. Without a medic, your team does way less damage. You are the most important person on your team as a medic. You want to avoid them by simply not peeking the sightlines. Snipers kill without warning (usually) and are not easily avoided. The main person you have to watch for on sightlines are snipers. One example of a sightline is near the second point of pl_badwater, where enemies can peek over the hill and attack you if you're standing to the left of the point. Sightlines are extended areas where enemies can see you. If a heavy starts firing at you and you're caught out, jump backwards, turn around, and strafe as fast as you can to get out of his line of sight. You can even 'surf' hitscan damage, if a scout meatshots you while you're jumping, you'll go flying.

+ Not only can you surf rockets, you can surf other projectiles as well, which includes the demoman's stickies and grenades. Fall damage only counts for vertical velocity, not horizontal velocity. If you have the option to not take fall damage, be careful to land INTO the obstacle, not on top of it. Be mindful of where you land, sometimes in midair you can use your strafe keys (a, d) to steer yourself into the face of a rock, where you can avoid taking fall damage. This will send you flying away from him, which can save you from almost certain death. + You can 'surf' a soldier's rocket by jumping right as his rocket(s) hit your feet. These tips are for medics in general, doesn't really matter on the format.

Tf2 medic shimeji