Get a good night sleep – The term says it well. You'll be constructing an impromptu deck so it helps you in choosing the right cards and also lessens the stress. Well, this one is not personally applicable to me since I'm working on a night shift unless the prerelease will be on a Sunday. I suggest you get at least 6 to7 hours of sleep.
Have an advanced reading of the cards – This is to lessen the hassle of deck building if you know already which cards to pick. Card are being previewed two weeks before so most likely the spoiler will be completed by the time of the Prerelease.
Bring a ballpen or any other writing pen – This is always a part of the requirement since you will be checking your card lists of what cards you've opened on the boosters and it is always a hassle to find one during the event. So my suggestion is be sure to have one with you.
Eat a full meal before the event – Prerelease tournaments will most likely take longer hours to finish than regular tournaments because of the time alloted for card listing and deck creation.
Bring extra basic land cards – I suggest you bring ten copies of each basic land card. The average number of lands used in a sealed deck is 17 to 18 so most likely you will use eight or nine basic lands of each of the two colors of your deck. But basing on the hybrid concept of Eventide, there's a big possibility of a mono color sealed deck.
So there you have it folks. I hope this can be a great help for you on this coming Prerelease. Just remember to be creative and enjoy playing with the new cards.
Till next time peeps...