For reference, Fux's rules for 2-voice first species (semibreve against semibreve)
1. Move to a perfect consonance in oblique or contrary motion -- never in direct motion (direct motion means both similar and parallel motion).
2. In general, contrary motion is preferred.
3. Use more 6ths and 3rds than octaves and fifths.
4. Begin and end the exercise with a perfect consonance.
5. In the first measure, be sure that the tonic pitch is in the lower voice.
6. If the cantus is below, the interval in the penultimate measure is a M6; the cantus is below, the penultimate measure will be a m3 (p. 28 bottom). This of course assumes that scale degree ^2 is in the cantus.
7. Voice crossing is okay.
8. Avoid "beaten" (batutta) octave, fifth, and unison -- approach to any of these perfect consonances by contrary motion with a leap in the upper voice. Of these, the beaten octave and unison are the worst.
Gauldin, chs. 3-5
1. Prefer separated voices to voice crossing. 27
2. Mix similar, contrary, and oblique motion. 27
3. Each part should be rhythmically distinct. 27
4. Begin with octave, unison, or perfect fifth. 28. For points of imitation, use "first notes" from the table on p. 13.
5. Within a phrase, unison only on weak beats.
octaves on weak beats, occasionally on strong
fifths on strong or weak beats 28
thirds and sixths used freeely, but avoid more than 3 of one kind in a row 29
6. Minim dissonances: PT and S only. PT on weak beats only. S requires minim preparation. Use 7-6 or 4-3; or 2-3 with dissonance below ("bass suspension") 30-31
SEMIMINIMS
7. Single semiminim only after a dotted minim. moves by step or leap down (Ex. 4-5C) from previous note. 36/38
8. Pairs of semiminims on weak beats only. 36 In counterpoint, semiminim NN: lower within any beat. Not upper. 43
9. Longer strings of stepwise semiminims may follow a white note. 36
10. Portamento (anticipation): semiminim on offbeat of the strong beats only. Almost always stepwise down from previous note. 37; 44
11. Lower neighbor notes are far more common than upper. 37
12. Nota cambiata 37-38; 44
13. Leap to semiminim after minim (not larger note). leap from semiminim to minim is against direction of previous line. 38
14. Leap from semiminim to semiminim within the beat for descent, to next beat for ascent. Always change direction. An easy way to remember this is "descend within, ascend between." 38
15. semiminim PT: unaccented may occur within any beat, rising or falling. Accented: first of a pair of semiminims on weak beat of the measure; always moves downward by step.43
16. In counterpoint, eighth-note pairs always stepwise. Do not use upper N. 39; 44
17. No direct octaves in two-part writing. Direct fifths are rare; they can be used only if the upper voice moves by step. 28