I know a lot of people that have been in this situation, fortunately I myself have never been caught by taking the right precautions. Here are some tips which may help you:
For the next month or so I would at least calm down the downloading (mainly large downloads since it's usually obvious p2p traffic), Supposedly they are a lot more likely to bring you to court if you get one right after another (I read you need 3) but I haven't seen anything to support this. It seems to be just random to me. Either way it's better to play it safe.
If you do not have a wireless router, GET ONE, If you get a letter saying you must go to court turn off MAC filtering and any wireless encryption, make sure to turn off all logging as well. (usually off/low enough by default on consumer routers) This way they cannot prove it was you. It could have been someone using your wireless. I read of a couple people that got away with it because of this.
Call your ISP, let them know it wasn't you downloading the files (blame it on anyone, say it was a friend's friend who came over, a neighbor, even say you don't know) and apologize for the inconvenience. If you don't feel comfortable lying just say you have deleted the file and you are sorry. Say that the website you downloaded it from made it sound like it wasn't illegal because many of them do. Maybe even say you paid to download it lol they will think your an idiot but who cares. Ignorance is no excuse but it usually makes this conversation go easier/the ISP is a lot more sympathetic than the law, especially since they still want your business.
Look into enabling encryption in your torrent client
Look into anonymous networks like TOR. I tried this and honestly it sucked ass. It was unbearably slow, public trackers are just not worth this nonsense.
Look into setting up IP Filtering, Don't listen to people who say these are useless. They are not bulletproof but they do help. If they cannot connect and prove you where actually transferring what they say you where they can't do shit. Just an IP Address is not enough, so these DO help assuming the IP is on the list.
Personally I only use private trackers, I do use Demonoid on occasion but I don't trust it too much, I only use it if I have to. Demonoid is like a semi-private site. Oh and STAY OFF TPB AND ITS TRACKER, It is not owned by the same people anymore. Even torrents you get from other sites, check it to make sure none of TPB trackers are in it (you can remove them if there are other trackers available)
Consider other means of downloading. I know I'm pushing Usenet again but it's worth it. You can't get caught. 256-bit encryption is no joke. You can put it through port 443 so it looks like web traffic (besides usage patterns) as well. Everything I do on Usenet from searching to downloading is all encrypted. There is no uploading either and apparently uploading is what you get in trouble for not downloading.
Speaking of encryption, when you go to torrent sites see if they support HTTPS, Chances are they are not monitoring all your browsing but just to be safe

All things considered, you are probably fine, I know about 15 people who got these letters, Only one had to go to court, and it ended up being dropped or something. (no one settled on anything it just went away)