Posture

Boxing has been a great help in getting at paralanguage. I find it rather easy to concentrate on the body language of my opponent when knowing I could take that right hook on my chin.

Besides the overall contribution one of the primary issues where I gained better understanding has been posture. Whether the opponent is leaning back or forward or whether I'm leaning in some direction. Whether I'm facing him directly or with a slight angle.

Posture can play a very important role in reading body language as it is one of the easiest signs to notice.
When talking with someone you can easily notice if they are leaning towards you which my be a sign of interest. Leaning backwards can be interpreted as "not really interested" or it can mean that the other party feels comfortable (it can even carry a hint of "territorialism" in a sense they feel at home).

You should also keep track of your own posture as any message you send with your body is received by the other party. These message won't always be interpreted but they will always be received and create a "gut feeling". So when seeming interest is to your advantage (a prospect, a flirt, or a friend) try to slightly lean towards them. This will also help create trust as you will be slightly getting closer (think proxemics) without entering the intimate area with your whole body, a rather nice compromise I'd say.

It's rather noisy

Noise has a very negative effect on communication and is a matter that should be dealt with.
Noise can be described as anything that is present in the communication apart from the communication itself. This can be coming from the outside such as background music, a failure in the GSM phone line or a loud conversation at the next table. But noise can also come from the inside, ever noiced how you stop listening when you start to think about something else? that's noise. Ever looked at the TV while your spouse was trying to tell you something? that's noise. Ever chacked your emails during the salespitch given? that's noise.
As you can see, noise is almost always present in some form or another.

We should be aware of the possible noises during communication and find a way to get rid of them if we want to be successful in delivering our messsage. We also need to keep the noise in mind when trying to get the most out of the communication, especially if you aim to understand if there is something else to it (a lie, a hidden feeling, a secondary agenda, etc...).

Physical posture can also be a source of noise.
Imagine trying to talk to someone as they are just leaving the office. You are both standing at the door, you trying to explain something, him only thinking of going home. You can also try to get someone sitting there with crossed arms to approach your idea. Again you and the other party are in totally different worlds as he is in a negative mindset while you try to pitch a new idea. A husband watching TV while his wife is talking about her cousin's newborn... Is there even a slight chance of any of that getting through?

In a perfect world removing any noise from the communication would be easy, you could just ask the husband to turn off the TV, ask the colleague to stay another 20 min, ask the other to stop checking her mails while you are talking or simply ask him to unfold his arms as you believe this will improve the quality of the communication.

But in the real world these could lead to direct confrontotions or an even more negative mindset.
The good news is that it's still rather easy to avoid the noise in communication. Wait until half time, rise the issue the next day when they are back at the office, give them a pen or paper so they have to uncross their arms to take it, etc...

The first rule about noise is similar to the rule about body language; know it exists and notice it.

You can spend a few days trying to point out noises in your everyday communications and you will be amazed at the amount of communication that is made in very "noisy" environments.