Species 1
Note against Note
Species 2
2 notes for every note
Species 3
4 notes for every note
Species 4
Syncopation, suspensions, using 2 notes against 1 note
Species 5
All of the above
Depending on the author, the expectation is that the melody consists of single time unit (i.e. all whole notes or all half notes, etc) and the counterpoint/counter-melody is to be written above or below the melody. Some examples will help to understand:
Species 1 ~ Note against note
[mp3]http://www.bandcoach.org/fp/audio/species-01.mp3[/mp3]
Species 2 ~ 2 Notes against 1 note
[mp3]http://www.bandcoach.org/fp/audio/species-02.mp3[/mp3]
Species 3 ~ 4 Notes against 1 note
[mp3]http://www.bandcoach.org/fp/audio/species-03.mp3[/mp3]
Species 4 ~ Syncopated Notes against 1 note
[mp3]http://www.bandcoach.org/fp/audio/species-04.mp3[/mp3]
Species 1 - 4 together
I have lowered the individual lines to better fit a full spectrum: The bassoon is playing the 2 octaves below how it was first presented and the Horn is playing the line 1 octave below.
[mp3]http://www.bandcoach.org/fp/audio/species-all.mp3[/mp3]
There are many rules (dos and don'ts) about how to write good counterpoint, so many that many people have written books on the subject (but not me

). They include discussion on how to prepare dissonances (non-chord notes) and the application of the rules to melody writing and composition in general. They also cover several melodic devices - units of melodic content - and how they should and shouldn't be used.
The rules are easily summarised into 2 or 3 pages and form the basis of most advice given about voice leading (individual lines in chordal harmony).
I may post this at a later date.