Poke'nests.

[Frenchfry]

Do you practise any black magicks other than necromancy?

Hey! That's Mr Pokemon's line!

There are 2 possible ideas:
1) o.5%-0.8% chance of finding a nest with every step in tall grass
2) 2% chance of finding a nest for every encounter with wild pokemon
Be clear about which option you are talking about to avoid misunderstandings. 

...Or, we could take any one of the other fifty plausible ideas. Besides, 2/100 is stupidly high. that would mean that you would reach a nest, approximately, every fifty encounters.

[DarK_SouL]

Funny this topic just keeps getting posts and I haven't checked it once.

Either way, this is a good idea... also I good story line would be if a pidgey is protecting ome eggs and you try and steal one then it attacks you are you pass out and the champion comes and saves you and you talk to them, then they take you to see the Pokemon League if you say yes.

Sorry 'bout no punctuation, I was just trying to get the idea out there.

[Mr Pokemon]

Do you practise any black magicks other than necromancy?

Hey! That's Mr Pokemon's line!

This.