Lúcio
Lúcio is a highly mobile hero. The Sonic Amplifier damage has been reduced in the new version while the close combat combo (RMB+V+LMB) also got nerf. However, Lúcio's speed boost and ultimate ability still make him one of the most popular supporters in the game.
When Amp It Up is in CD, Crossfade provides very limited healing effect, but its speed boost can still help the team pretty well. That's why speed boost is recommended when Amp It Up is in CD, or you have other healer in the team.
When the enemy heroes such as Pharah, Reaper, Genji, Hanzo and Soldier: 76 use ultimate abilities, it's a better choice to boost speed to move away than boost healing. On the other hand, when Lúcio's speed boost is still taking effect, his allies can use ultimate abilities for better effect.
Another time to use speed boost is the time you have multiple allies at respawn point and speed boost will help them get back to the center of battlefield fast.
You should try to use ultimate ability when your boost ability (E) is in CD so you can make sure your allies are safe.
Mercy
Apparently Mercy will be the prior target for the enemy team, so she should make use of the Guardian Angel ability to fly to an ally to protect herself. If you can't find an ally around you, Caduceus Blaster is still a trusty weapon to use to survive for as long as possible.
Speaking of healing, it's important to switch between different allies and identify who has the lowest HP.
Mercy can resurrect (ultimate ability) all dead allies nearby to full health, and that makes Mercy a hero that can turn the tide. Therefore, the suggestion is to ask your teammates to stay as close as possible so that you can make the most of your ultimate ability.
Zenyatta
Zenyatta has the highest DPS among all support heroes but he's obvious underdog facing against Offense heroes.
Orb Of Destruction is an ability you can use as you take cover at the corner. After you attach Orb Of Discord to an enemy target, you can tell where the target is. Orb Of Discord's damage mechanism makes this ability deadly to enemy tanking heroes.
Symmetra
If Lúcio is also in your team, make use of his speed boost ability to deploy Sentry Turrets at the key positions. Before encountering enemy heroes, get Photon Projector's charged attack ready to damage enemy's Offense heroes.
After killing an enemy with Photon Projector's beam, keep pressing on the left mouse button (therefore the damage won't reset) and search for the next enemy quickly.
If the opponent team has highly mobile heroes such as Tracer and Genji, you better place the Teleporter at hidden place even you have to sacrifice a bit of convenience.