If I score a kill and have like half air left should I return to my Teams lines or keep on
going?

I'd say that rushing is fine, just make sure you've got a high level torpman (I had a
level 45 when I got my first SS), and learn how fast the torps are. That'll let you
basically take out anything other than a sub with a single shot. 20k should be easy to hit
in attack. Subs you have to be a little more careful, but the proxy torps make it not that
difficult. You'll find it usually disolves into two subs pointing right at each other,
crit diving as needed. My suggestion: When you think they're in range (before they even
show up on sonar), shoot a slow torp right at them to force a dive and hopefully some
panic return fire. Crit dive if needed, then launch torps set to fast. Repeat as needed,
and you should be able to kill an SS or two each round as well as all the DDs and CLs.

always sink first, what most likely is going to be a threat to you. Km is good for this
kind of circumstances due to its proximity torps. but for the other nations trying to sink
a ffgoing t 50-69 knots, is not that easy.

With all the ASW running around it'd be suicide to ignore smaller ships. If their just
gonna sight you then fine but most of the time be ready to eat about 20 HH's if they get
close enough

It is very common to run out of air next to BBs when you're in a SS2. Here are some
tips:

-Make sure that you have a Planesman at full crew
-Only dive once fired upon by another BB, if it's bad spread then you may keep going
until
a shot almost hits you
-Do not overheat next to BBs, because that will make yourself visible
-Don't waste time with DDs, unless they piss you off
-Get an engy to go as far as possible in the begining

I'm new to this forum thing, so I hope that you get better and have lots of fun!

P.S. Reading all your comments are great! I just remembered that killing submarines
yields bonus experience points, which would be wonderful for you to get your SS3
ASAP.

-Mikiya