Pre-Game in my definition is the first 1-5 minutes of the game. In general not a lot of things happens but if you make something happen it can be very impactful. The following list are just things I've seen great teams do to dominate the pregame.
Let me just start off with a disclaimer. Doing this strategy pre-level 30 and or not coordinated as a group of 5 can and will be fatal. These strategies are meant for organized play.
1. Getting Elder Lizard Buff/ Ganking With Elder Lizard Buff.
Getting the Elder Lizard Buff at level 1 can be highly advantageous for any carry hero. Having the buff allows you to harass better, farm better, and possibly get you a first blood. The saying as it goes with my team is, "If you have the lizard buff, you better get first blood." Generally, when we attempt the lizard buff we also expect the possibility of being ganked. So the strategy here is, although we do not need 5 people to get it, we will roam as 5 anyways.
The lizard spawns around 1Minute and 36Seconds if your game loaded correctly. Knowing that you have about 30 seconds at the beginning of the game to get your items and position yourself correctly. First you want to all go to the lizard as a group but run past it and hide is the brushes. Doing so will allow you for a counter-gank if the opposing team wants to organize a gank on your lizard. At roughly 1 Minute and 28Seconds if the other team does not show up you should get to position of get the elder lizard.
Afterwards the person with a teleport will teleport to the furthest lane from where the Lizard is, the soloer will run mid (mid is generally solo), then 3 people including the person with the buff will run to the lane closest that is not mid. The 2 people without the buff can show themselves behind the creep while the person with the buff can run to the river and hide in the brush. I generally initiate the engagement when I see a creep closer to our side that is at 1/3 hp because most champions will move forwards to last hit it. Remember when you initiate you want all 3 to move simultaneously. You want the stunner to stun first if you have a stun.
To ensure a successful gank or prevent a fail, here are some additional tips.
1. Keep tabs on heros with flash and heal as their summoner skills. Flash will allow them to escape and heal will make them harder to kill.
2. Have the heros concentrate more on harassing than killing creeps in lane to lower the gankee's HP while you position yourself because you want them low and the creeps on your side.
3. You don't always have to gank the lane that is closest to lizard buff. Because some lanes are squishier than other. I leave this to your best judgement. But I want to find heros that have less than 700 hp at level 1. But lesser is better.
4. The buff should go on an Ashe, Twitch, Warwick, Corki, Yi, Teemo, Tristana, or Katarina.
5. Its ok that the buffs go to your solo, it will help him dominate his lane.
6. You dont always have to gank.