After playing this game (while drooling over sexy pirates) for about 2 months, I've made several observations to the brawl points system, which is a wonder to many of us. The following observations are from sole observation, and cannot be supported by any form of data, so please be lenient in criticizing anything.
In addition, I would greatly appreciate it if some of the more experienced players could support or refute any of these observations, since they've obviously had more experience than me. Thanks!
1) Brawl Points increase by 1.5x when in a 2nd or 3rd place Nation.
Kinda obvious, because the help menu flat out tells you, and there seems to be no difference of BP between being 2nd place or 3rd place.
2) More Brawl Points are earned for a 5-0 win, than a 3-2 win.
Another obvious observation by many players, just setting up two strong pirates and getting a strong assist to defeat a high leveled player is effective in some cases, but not always. It's about finding that balance.
3) The higher level the opponent, the more brawl points he will give.
I personally don't like this rule, because one of my friends is an extremely powerful brawler, but he is only level 34, while I'm 51. Level does affect how much Stat points you have, but this is barely an advantage in many situations.
4) Brawl Points DECREASE for consecutive attacks.
Let's say player A attacked player B, won 5-0 and got 1500 BP. If player A attacks player B again, player A will (even with the same cards/skills/wins), will receive a slightly lower amount of BP; about 1450. This effect is cumulative (aka, the BP you get will continuously decrease), probably in order to prevent the defending player from being overwhelmed.
5) Brawl Points INCREASE for defeating a player, who has previously defeated you.
It seems that in cases where a player is attacked multiple times without counterattack and lost all those matches, the player at hand may perform a "revenge" for a raised amount of BP. However, this "increase" seems to be limited unlike Rule 4.
6) Brawl Points earned corresponds to enemy defense.
Say you have player X with 24000 total defense, and player Y with 10000 total defense, and both players are of same level (Refer to rule 3). If you can manage a 5-0 win with both opponents with the same cards, you should definitely attack player X, since defeating him will give more brawl points.
7) *UNCONFIRMED!!!* Brawl Points INCREASE with the number of skills and combos triggered.
This is from personal observation that when I trigger a combo or skill, I tend to receive slightly more brawl points than if I did not. While this CAN relate to rule #8, it's unconfirmed anyways, so I place them in different categories.
Brawl Points INCREASE with the value of your total Attack.
This observation stemmed from two attacks made towards my defense crew, which currently has about 28k defense. I have observed two attacks to my crew, and disregarding rule #7, this was the result:
Player A had 66000 Total Attack, gained 3300 BP
Player B had 47000 Total Attack, gained 1400 BP
Please realize that these numbers were obtained during a guild brawl (hence it seems a bit high), and both players received the 1.5x bonus, while attacking me for the first time. The key point is that my defense crew remained the same throughout the entire brawl, which led me to the creation of this theory.
9) *UNCONFIRMED!!!* In a guild brawl, winning against the guild master gives more brawl points than if you won against a regular member with the equivalent stats at equivalent conditions.
10) During a guild brawl, you will earn x2 the amount of brawl points than if you performed a brawl outside of it.
Thanks to TheRealShrad for reminding me about this. If you want to be your guild's master gunner, you better participate in these GvGs!
Thus ends the list of theories created from pure observation. Comments, additions, and corrections are welcome and greatly appreciated.