As long as you've set enough max connections (200+) but not TOO many (<=500, generally, is a good idea, or you may start to see lag in your OS), most of your torrent client's settings shouldn't need many changes. It's a good idea to set the max connections per torrent to the same as the max total, btw, so if one (or very few) torrents are active, they can use as many connections as possible, up to the total limit; this can benefit both up and down performance. Increasing the number of upload slots per seeding torrent (usually 4 is the default) at one time is also potentially useful. None of these settings, of course, will enable you to upload when nobody is downloading from you; the only fixes for that are time and careful selection of torrents, I'm afraid.
It's a good idea to turn on disk caching in your client, BTW, which will lessen "disk thrashing"; in other words, it will lower I/O activity, which means less stress on your HD(s).
Choosing torrents that are popular can help a lot, but isn't actually necessary; I *never* download a torrent I don't actually have some interest in, and my current ratio is 1.791 (3450.49 GB up:1926.06 GB down). The single most useful assist to improving your ratio, honestly, is "Power User" status, which is granted once you have DOWNloaded at least 25 GB and have at least a 0.5 ratio. Power Users have access to newly-granted torrents significantly before lower-status/public users, giving you a chance to upload a good amount to them once they also gain access to the torrent.
Good luck! And props for asking before you get in trouble, by the way.
