Honestly, I'm not sure. But I think you get S ranking, and you hope to get lucky. That's what I did and I got Vileplume and Sceptile.
When the respective bosses are beaten in the past missions, the slates will crumble.
dude if u ever get one plz mail me at it plz id : pokemon.freak44@yahoo.com
after Celebi sends you into the past for a third time you can do "multiplayer" missions in the past (you can do them alone but with a friend is faster also the missions have a time limit), some of these missions involve battling the Pokemon on the slates and when you beat them and go back to the future the slates will break opening a the path for you.
They have Pokemon behind them, but to open them you have to complete missions on ranger net ( their not legends or special Pokemon just ordinary ones.)
guardian signs
Pokémon Ranger: Guardian Signs (Part One) and Pokémon Ranger: Guardian Signs (Part Two) or SS022 and SS023
its for unlocking new partners in multiplayer mode
The Elder Guardian in the ocean monument is the third boss.
fall city is unt in Pokemon ranger guardian signs
Guardian Signs comes out in the UK and all of Europe on 5 November 2010.
You can get honchcrow in guardian signs in the sky near aqua resort, sorbet mountain, and rainbow dais.
do quests and catch legendary Pokemon to get signs