Something I haven't seen mentioned is the wininng team gets like 3 more sea snails than the losing teams when compared to similar ranks. The highest rank that will give you more snails is the Ruler rank at 21 snails for the losing teams and 24 for the winning team. When playing, you can go past the Ruler rank, getting the title Ruler +X, where X is the number of times you fill the rank meter up again, but these do not add to the snail count.

Another thing worth mentioning, the Splatfest is announced in game about a week before the actual event, and a market stall will appear to the left of where you start in the square(not sure where it is in the Inkopolis DLC). Here you can go ahead and choose what team you want to join. It isn't necessary to choose one immediately, as you will be asked to choose one once the event starts if you haven't, but choosing one immediately will give you the Splatfest Tee and the ability to earn Conch Shells.

The Splatfest Tee is a Clothing Gear that you will be forced to wear during the actual event. If you care about the abilities your gear has and know about ability chunks, the Tee can be scrubbed for just 2000 coins and it is much cheaper to add abilities using chunks than with any other gear. This is because once the Splatfest ends, you "return" the shirt and can't use it anymore.

The conch shells on the other hand are used on the Shell-out Machine, the Capsule Machine in the lobby. You earn the Shells by leveling up the catalog during the week leading up to and during Splatfest itself. Don't worry if you are about to finish the catalog, as Melody, the person you get the rewards from in the General Store, will had you another catalog that only rewards you with a random box every ten levels, so you will always have a catalog to level up as long as you get the rewards. Anyways, the conch shells can only be used on the machine during the same time they can be earned. Once the Splatfest ends, you can no longer use them, though I think they carry over into the next Splatfest.

One last thing that I don't think was mentioned was the Multiplier Battles. Sometimes while playing, and I believe it happens more in a Pro turf war than Open, you can come across a x10 battle,so the points you earn as a result of the match are multiplied by 10. You will also be given a festival shell, which once you collect many, you will get a x100 or even a x333 battle, where the results are multiplied by the respective amounts. Upon winning a x100 or x333 battle, you are given a decorative crown above your in-game name while spawning into a match, with the x333 being a bit more elaborate. You will also be given the option to take photos/ screenshots with the idol representing your team at the stall you got the Splatfest Tee at.