[!!!!!HELP!!!!! how do tune a speaker box???]

wellthe title sais it all, how do i tune a speaker box when i make one.? i always use eyemeasurement and they always come out great (better than proboxes lol) but yea, is there a formula or rule i follow.??? help will be very appreciated

[96' Impala SS in the making]

Hey, whats up guys im Ralfi and im not new to SMD but im new to being a member if tat mkes sense, but anyway. I am at this moment in my life saving up for my next car, which is going to be a 1996 Imapala SS and dont worry im not gona make it a ansta ass gd out ride and just slap rims on it...NO. im going to replace everything such as motor rebuild, new alt,the big 3, new tranny (for the rims) and etc... but yea as far as the system goes, i dont even know what the hell kinda setup i want yet, but trust me i am a pro at building boxes and hooking up systems and what not so i know my share of car audio knowledge lol but to start off, i for sure want 2-15" SMD subs but as far as amps go, idk what i should go for (thinking about RF) b/c whatever brand i buy the amp is what the brand for everything but the subs will be, such as door speakers, tweeters, wiring and so on. Also, if yo dont know what the trunk of the impala looks like, just know that its huge and you can fit a bus in there, so as far as the box goes, any recommendations on how bi i should make it and the port.????? well any advice and help will be greatly appreciated.!