For Tier 4 and up (unless there are other DDs that can 1 shot BBs):

I have seen this quite a few times where the DD seems to be reluctant to get nice and close to the CV, often torping from behind (wide,contact) or proxy. The easiest way to torp a CV is either narrow(preferred)/wide(if not confident) contact torps from the front left or right. So it will hit the side of the CV no matter if they stop or turn. For smaller CVs and you're not confident maybe wide contacts are needed. Line up your stern with his bow and let rip. Make sure youre at appropriate range (close enough for 100% accuracy but enough for activation range).

If the CV has an escort and you get close enough to torp but failed to kill it, it's best to stay inside the CV if it's big enough or stay on the opposite side of the CV to make the CV take the hits. Longer CVs are easier to hide inside rather than the smaller,thinner ones. It is also a good idea to hide in a CV as he may have bombers above so sometimes they try to bomb you but you can run inside their hull so they bomb themselves (it's happened before, I laughed a lot).

For a BB it's quite different as one full broadside (gradual fired where all of them hit you) will kill you, however if they are firing salvo you have a chance. If it's a large BB with guns spread on either end you can just maneuver to the middle of the BB so the guns will mostly miss you (you may get 1 or 2 hits but at least you live). Though, some BBS are quite manueverable it's best to launch the torps as close as possible and also during a turn. However do be careful of the activation range as you may look like you're at the perfect range but you are actually too close (many BBs have lived due to this estimation). Do be careful of the BB's smaller guns as they do hurt a lot. If you cannot get infront of the BB, then you will most likely die unless there's another juicy target for him. 

For the BB, it's the same as the CV. Get a head a bit, at least where you're mid section is in line with his bow (if youre parallel), if he's turning then as long as youre bows are lined up it should work. However you may miss during a turn in the opposite direction. Also remember to aim ahead, it never pays to aim behind.

Examples:

Leading BB target from the front

Leading BB target from the center ( riskier if they start turning as it could just pass the bow)

The easiest way to kill a BB would be to do a sneaky border run and then come in on the opposite side of the engagement. That way they're 14+ inch guns will be facing the opposite way (the majority depending on ship). Then you close rapidly and launch torps when in position and range (better when the ship is stationary, do becareful of the super acceleration of some ships). Then run like a little b!tch because the other BBs will be after you.

(These are from personal experiences)