How do you prevent yourself from pushing the shots long at the net? Sometimes I accidentally hit a lot of my kills long.
You should already be gripping higher up the cone when playing in front in doubles. So that would give you less power with more speed. Second, you should remember that speed is more important than power when up front. So use a compact swing with less shoulder muscles.
Shots from the net should be hit with control, not power. Think about placing/pushing the shuttle where you want it to go, rather than hitting it.
Are you getting to the shuttle soon enough? Gripping up & a more compact swing (barely more than a tap) will help you to take the shuttle earlier, thus getting a steeper angle on the kill. Also, are you approaching the shuttle with your racket up already? You could be losing crucial tenths of second having to partially raise your racket.
hmm... I may be getting to the shot too late perhaps, because i feel my racket is tilted a little upwards/forwards instead of downwards. So basically need to keep the racket up beforehand?
Yes. One of the essentials of net play is to expect a fast and flat (just above the net tape) shot from your opposition. Therefore, have your racket ready. Also, try to take the shuttle as far in front of you (i.e. panhandle or thumb grip). That way you can intercept closer to the net, which will be earlier/steeper etc.
3 things I can think of, 1.) Your swing needs to be small and compact, no need for a big swing and tons of power as you may hit into the net, out or hit the net with your racket. 2.) Get there early, the shuttle won't stay above net height for long. 3.) Finally, and this is maybe a bit less obvious, if you're in doubt of hitting it out the back, hit cross court, as it's a longer distance. This is helpful with clears and a fast shuttle too.
You might be getting a bit over-excited, especially, when the game becomes faster, and start losing control of the game. It is important to be able to change directions of returns in faster/flat rallies, not trying to finish the rally by just returning the shuttle directly into the opponent. It is also more of a footwork problem, rather than the way you hit the shuttle. If you are not fast enough and cannot get to the shuttle close enough to be able to change direction of the shot, than you might need to work on it. I also agree with the comments above about the grip.