Originally Posted by http://azureuswiki.com/index.php/Force_Start
When you right-click a torrent you can choose Queue or Force Start, among other choices. Force Start is used for starting a torrent manually. This torrent will be out of order from the queue and not adhere to Good settings.
Many newbies think Force Start helps to let them download 10 or even more torrents at once, because they don't like that some torrents are queued.
But Force Start only seems to allow this. Because it overrides your (hopefully) Good settings, using Force Start will spread out your upload capacity over too many upload slots - and your overall download speed will actually suffer.
Please use the Good settings page to calculate proper settings. Doing that and using Good Torrents, having a good Average Swarm Speed, is far better than using Force Start.
The Force Start setting is disabled in Beginner Mode. This is because frequent misuse caused confusion among naive users, and too many help requests. Therefore, only users who have set their Options Mode to Intermediate or Advanced will see Force Start when right clicking.
The setting is modified by Azureus > Tools > Options > Mode