I'm not that good either but I improved somewhat doing this:
1) create a "test" career at the very beginning of the war
2) find yourself a suitable target, a single merchant on a fine day is ideal
3) save the game as soon as you spot the target
4) stop there, pick up pen and paper and plan your attack in advance, write down a checklist of the things you are going to do. My advice is to run you first attacks from very close (600m or less) and an ideal angle (90°, either port or starboard)
5) do every step, take your time by pausing the game when needed and write down the data you got (target heading, speed, torpedo settings, and so on)
6) write down (or take a screenshot) of your TDC settings just before the attack and write down what you expect to happen (i.e. hitting the ship right under the funnel)
7) open the torpedo tube (I find this difficult to remember)
8) fire your torpedo!
9) cross your fingers! this is a very important step!
10) see what happens, write it down and compare it with what you expected trying to figure out what was wrong (i.e. wrong extimated target speed, incorrect AOB and such)
11) add or remove steps from your checklist if need be
12) save and exit, reload the engagement and run it again trying to fix what went wrong
13) rinse and repeat
14) once you get it right most of the time, change your attack plan (i.e. increase the range, attack from ahead or from astern with less than ideal angles, give yourself less and less time to gather the data, etc)
15) rinse and repeat
16) when you are confident on your results let yourself be spotted so that your target will be zigzagging and...guess what?...see below
17) rinse and repeat
18) play as much as you can and have fun!
Some people have the talent, others need practice...I need practice and lots of fingers crossed!
Have fun!
