[GoldenRivet]

You get renown for...

1. sinking enemy merchants
2. sinking enemy warships
3. downing enemy aircraft
4. reaching assigned patrol grid
5. remaining in assigned patrol grid for 24 hours
6. actually returning to port instead of hitting escape and selecting end mission

you lose renown for...

1. sinking friendly or neutral merchants
2. sinking friendly or neutral warships
3. downing friendly or neutral aircraft
4. sinking hopsital ships

i dont recall the exact figures, ill try to locate them for you, or someone else will post them. but each ship has its own renown value.

if i recall correctly - blowing a hospital ship out of the water will earn you NEGATIVE ten thousand renown points (yes... -10,000)... it would take several perfect patrols just to get back to zero renown for that mistake.

edit:

reaching patrol grid gives you 200 renown points
staying there 24 hours gives you another 200 renown points
actually returning to base to end you mission yields 100 renown points

each individual ship has its own renown value which can be found by locating the ships CFG file in your sh3 "sea" folder in the main SH3 directory,

for example an illustrius fleet carrier is worth 900 renown points, and a large merchant would be woth about 500 renown points etc