A tip for new Kalista players, from a support main
Time and place.
This advice is useful for ARAM as well as Summoner's Rift.
<-- see this thing? You use it on an ally to become your Oathsworn. You have an ultimate now, or half of one while they get the other half because sharing is caring. You get more damagez in lane. You have a true ally, a friend, a slave partner who's got your back and stuff.
But.
While the initial bonding animation is cool and thematic and stuff, they are not immune to taking damage.
Places you want to bond at: -the fountain (SR/ARAM) -the tower (SR/ARAM) -a warded jungle (SR)
Places you don't want to bond at: -in the lane during the laning phase (SR) -in front of your enemies' tower (SR/ARAM) -in range of your enemies' tower without minions (SR/ARAM) -an unwarded jungle (SR) -in front of Blitzcrank/Thresh (SR/ARAM) -a teamfight (mostly ARAM, but SR too)
For ARAM Kalista players, another free tip: just because someone is playing a "support" champion does not mean you should respond to that kneejerk reaction and bond with them. I highly recommend asking instead of forcing it on someone, especially at a bad time and place, and choosing the best champion, not just support, that your kit would most compliment. While giving Soraka extra peel for her bananas is not a terrible choice, giving Sejuani a powerful engaging tool might be a better choice. It really depends on the team, the individual players, as well as your confidence.
In the right hands, Kalista is an excellent addition to the team instead of just another cookie-cutter tower shredder. A little etiquette and strategical thinking goes a loooong way with her, more so than simpler AD carries.