If you have Blitzcrank, Nautilus, Ryze, Maoki, Ahri, Morgana, Janna, or Taric you should try to invade because all of these champions can learn long range CC at level 1. Meaning your entire team can hide in a bush and wait for someone to poke out and instantly stun them. Which usually leads to a dead champion unless they are able to instantly flash behind a turret. Most of the time in low-medium ELO people are so surprised that someone is invading that they flash into a wall and waste it. Leading to first blood and even additional kills if their team comes to help because it turns immediately into a 4v5 and you know you have a hard cc at level 1.
You should always leave at least one minor camp creep up, especially since the change in jungle not having those big neutral creeps re spawn really slows down a jungler. If you are able to steal a buff you should kill the entire camp and write down the time that it died so that your team knows exactly when it re spawns so that you can steal it again.
*Summoners Rift Neutral Creep Spawn and Re-Spawn Timers *
Spawn time/Spawn period
- Anc Golem 1:55 5:00 -20% CD, +25 flat mp5, +0.5% Max mana
- Lizard ....... 1:55 5:00 8/16/24% Slow, 10-50 True Dmg Twice over 3 seconds
- Dragon ......2:30 6:00 +400XP, +130G*, +130XP*
- Baron ....... 15:00....... +900XP, +250G*, +50 DMG/AP*