Honor rating is one of the important factors in Mount and Blade, including Perisno. It acts like karma and determines player's relation point with most lords.
Becoming Honorable[]
Player will be honorable if his/her honor rating is +1~. However as said by many players, being honorable is difficult in Perisno and it is true. Thankfully in 1.1,3 honor can be balanced without too much difficulty, Honor can be gained by releasing lords who are defeated in battle, rescuing captive lords, releasing conscripted prisoner (this is new in Perisno, player can capture enemies by knocking them unconscious and then take them as prisoner. After that talk to the prisoner and select the second option, player will release the prisoner and increase honor rating +1 after releasing 6 prisoners) also if player has strong funds, player can go to Priest Felixius or Priest Fyurs pay either of them 2000 aurums (first option) and player will get +2 honor and relationship with the respective religion for each payment. Becoming honorable is very beneficial in the later game, especially once the Kingdom of Perisno is formed, as each +10 honor rating will gain 1 point of relation with Upstanding/Good-Natured lords, at 1000 points a 100 relation is guaranteed, making them an asset for the kingdom.
Here's some videos showing how to raise honor:
Priest Fyurs and Felixius: https://www.youtube.com/watch?v=BWznAQRjWd0
Prisoner: https://www.youtube.com/watch?v=gKRjiGiCL_g
Becoming Dishonorable[]
Player will be dishonorable if his/her honor rating is -1~. Honor rating can be reduced by looting, taking hostile action to villages and killing prisoner (talk to prisoner and choose the third option and then choose the first one to confirm killing the prisoner). However, being dishonorable also hurts very much in later games. Not only Upstanding/Good-Natured lords, but martial lords will also hate player very much. At -30~ points don't expect those lords will accept vassalage to player's kingdom.