Don't. Do NOT AT ALL.
Unless someone else has already added the tracker, you won't find anyone. And if they've just added the tracker, guess what, you'll already see them on the tracker that came with it.
If you're really sure there's peers out there you're not seeing, then turn on DHT. It's that simple.
Just adding trackers however not only doesn't 'speed anything up' (trackers have NOTHING to do with speed, just like the number of phone books you have to look a phone number up doesn't make a conversation any faster) you're sending out more traffic, which means you've less to use for transfers.
You're also adding bandwidth and load to trackers, for no gain, so you're actually harming trackers.
Still think it's a good idea? (if you want to see the maths just from TPB putting 4 tracker on every torrent, I did it here. With 50M peers, it works out about 20Tb of useless duplicated data PER TRACKER, PER MONTH.
I believe you can do this on qBitTorrent. There is an option to "automatically add these trackers to new downloads." – Doug – 2018-01-08T00:00:42.220
Is the torrent present on all those trackers? Adding a bunch of useless trackers to every torrent might not cause any problems, but it might slow down downloads as the client makes repeated useless requests to trackers that will then reply with a "torrent not found" error. – Karan – 2013-01-13T19:34:47.503
@Karan: ok, so maybe a way to provide a list, so that whenever I add a torrent to my client he asks me which trackers from that list I want to add? – JNat – 2013-01-13T19:57:26.717
You'll have to see if someone's coded an app for this, or make one yourself. Perhaps it might be easier to do this with the uTorrent WebUI, but again I don't know if a solution already exists. I think you can add trackers to multiple selected torrents in uTorrent, but that will remove other trackers that exist already. – Karan – 2013-01-13T20:01:29.510
@Karan: yes, you can add trackers to several torrents at once, but uTorrent overwrites the existing ones. – JNat – 2013-01-13T20:03:02.537
Yeah, that's what I remembered it doing. – Karan – 2013-01-13T20:03:45.750