Stick with your team, cap or defend objectives, revive teammates, drop resupply bag at every opportunity, spot enemies every chance you get. If you're the squad leader, mark objectives you or your squad caps. I played Support almost exclusively the first season, frequently in the top 5 or top squad. Really not that hard...
EDIT: Try this loadout. Defibs, Resupply Bag, Resupply Pouch, Smoke, gun of choice. Like I said above, always be dropping resupply bag around your teammates. Defib or revive your teammates... toss smoke on top of them if they're in a dangerous spot. But in addition, toss resupply pouches at teammates too.
I appreciate the advice, but I’ve been playing Support in every form since Battlefield 1942. I know the role well. If I’m being honest, the meta in the later seasons has clearly favoured Engineer for points — they’re almost always sitting at the top of the leaderboards. That’s been my consistent experience, anyway. Tweak the scoring to properly reward the Support role and more players would actually pick it… and more importantly, they’d drop ammo. This isn’t a dig at any other class per se. Every role matters. I’m not here to start a flame war regarding them.
All good. I've also played mostly Support since BF3. I would also recommend Breakthrough, as this game mode tends to funnel players naturally into choke points, giving you more opportunities to supply, rez, etc.