Firstly uTorrentis my current fav torrent download software. Its the best software in smallest package.
Download: http://download.utorrent.com/1.7.5/utorrent.exe(214kb)

After trying out many different settings I am just sharing my best configuration for utorrent. Obviously your best config may be different because of your network and hardware etc.

Coming stratight to the point, I have 450kb/s download with 100kb/s upload. You can check your speed from http://www.speedtest.net/ and make settings accordingly.

Options>Preferences:
Global maximum upload rate (kB/s) = 10
√ Allow incoming legacy connections
Global maximum number of connections = 128 (If you don't have bandwidth then more connections dont mean more speed)
Maximum number of connected peers per torrent = 16
Number of upload slots per torrent = 2
√ Use additional upload slots if upload speed < 90%
√ Enable DHT Network
√ Enable DHT for new torrents
√ Enable Peer Exchange
√ Enable scraping
√ Pre-allocate all files

Advanced Settings:
peer.lazy_bitfield = *true
net.max_halfopen = *40
peer.disconnect_inactive_interval = *600
diskio.write_queue_size = *2560
diskio.read_cache_size = *2560

I have doubled my speed after these settings. And please note that there is a 8fold difference in kilobit and kilobyte.(1kilobyte = 8 kilobits).It took me a while to understand the best settings so I am sharing with you. A well seeded torrent will download at speed of 18.

SHORT NOTE: Seeders are people who have already downloaded the file and peers are number of people who are currently downloading the file. You should have more seeders for good speed.

You can download torrents from here:

www.isohunt.com

If you found this useful then don't forget to reply so that this thread remains on the top and other people also benefit from it.