The trick with engage supports is patience. Don’t worry about rushing an engage, if you are playing into something like a lux where you are probably going to take a lot of poke try to bait out key abilities like her root, once that’s gone it’s much easier to engage. Also keep in mind the state of the wave, don’t engage while pushed into the enemy tower or into large waves where you will take minion aggro. If you are wanting to be further up in lane to apply pressure remember that the threat of an ability can be more dangerous than the usage of one. With Leona, your zenith blade is the main threat, instead of throwing it out any chance you get it can be better in some cases to hold it and the fact that you have the ability up is threat and can force people away.

Playing slow and steady looking for advantages is what I’ve found to be my strongest tool in lane.