There are two things to look out for when hunting Pokemon.
1) The number of feet - the number of footprints drops from 3-2-1-0 the closer you are to the Pokemon.
2)The Pokemons position on the nearby pokemon list (or Poketracker as i refer to it). Top left is closest to you, bottom right is farthest.
When I am hunting a specific Pokemon I keep the Poketracker up , if the silhouette moves left I know I am getting closer and if it moves right I know i am getting further away. Think of it like a very sophisticated version of marco polo or Hot&Cold.
I think you will find this link helpful: http://www.pokemongodb.net/2016/04/pokemon-go-types.html
It has a chart at the top showing what percentage of Kanto pokemon belong in each type. Below, it shows a list of all Pokemon in the game and after that there is a chart showing what type of Pokemon to expect in various Biomes.
Happy Hunting!
Possible Types
Normal
Boundaries, Landuse, Places, Roads, Transit, College, Commercial,
Common, Footway, Hospital, Hotel, Library, Major Road, Minor Road,
Pedestrian, Pitch, Playa, Recreation Area, Retail, Runway, School,
Sports Center, Stadium, University
Grass
Landmass, Farm, Farmland, Farmyard, Forest, Garden, Golf Course,
Grass, Meadow, Nature Reserve, Park, Path, Playground, Residential,
Wood
Bug
Farm, Farmland, Farmyard, Forest, Garden, Golf Course, Grass, Nature
Reserve, Park, Path, Playground, Wood
Water
Water, Basin, Canal, Dock, Drain, Glacier, Lake, Ocean, Reservoir,
River, Riverbank, Stream
Flying
Farm, Farmland, Farmyard, Forest, Garden, Grass, Nature Reserve, Park,
Wood
Rock
Building, Landmass, Highway, Industrial, Parking, Quarry, Railway,
Urban Area
Ground
Landmass, Ditch, Land, Parking, Playground, Railway, Taxiway, Urban
Area
Fairy
POIs, Cemetery, Place of Worship
Dark
Cemetery, Cinema, Theatre
Steel
Building, Railway
Dragon
POIs
Ghost
Cemetery
Ice
Glacier
Psychic
Hospital?
Electric
Industrial
Fire
Residential?
Poison
Wetland
Best Answer
These steps represent the distance from the Pokemon currently.
Each footprint represents 50 meters of distance, starting with zero footprints means the Pokemon is no more than 50 meters away.
For example, one footprint means the Pokemon can be 51-100 meters away in any direction. Three footprints means the Pokemon is at most 200 meters away.
Note, however, that these numbers do not reflect Pokemon spawned through Incense or Lure Modules. Additionally, there is (at the time of writing - version 0.29.0) a bug that causes the distances to not update properly, causing the approximate values to be slightly "off."