My simple guide for beginers
Other important thing is strengh of signal. Some submarines have it in Active intercept station. Last 3 (red one) lights means - you have trouble.
Some subs have long range HF (ex: russian SSN) - it is good tool for ranging danger:
1) mark
2) see it on map
3) place own mark "+" (enter)
4) delete from map original "HF mark"
5) go to HF station and mark again
...and so on
OFC it helps when your sub is heading to enemy
Evading is quite complex thing. You need experience and luck. In MP session enemy player can guide torpedo via wire - remember that!