How do peers download torrents so quickly, like my download speed is 30 kb per

First of all, it depends on your Internet Service Provider. Maybe you should check you ISP bandwith speed. Mine is 1 Mbps. if you can only download at 30 Kb/s, then your ISP bandwith speed must be 512 Kb/s or there might some restrictions from your ISP including download activity. If this is happened, you must change your ISP if you want to download at high speed.

Second, it depends on the seeds from the torrent. No mater how fast your ISP is, if the torrent seed is minimal, you won't get your file at high speed.

Third, try this software for your 'instant downloading'. http://www.freedownloadmanager.org/download.htm , FDM not only download your torrent but also speed it up.

and make sure your computer is in the best shape. Don't use an outdated computer.