Something I've done every fishing tournament is to have my non-combat pet Egbert out. His constant running around and splashing serves as a distraction to others, especially those that rely on sound to hear their bobber. I've noticed on more than one occasion that a rival will mistakenly click on his bobber when Egbert runs near the pool.
And the most success I have is fishing the 6 pool nodes at the Ruins of Aborraz. Fewer twinks and when there are no pools spawned, everyone rides south to find another. I just patiently position myself at the tip of the land between the 2 sets of 3 proximal nodes and wait for the pools to appear. Yes, I lose a minute, but when the pools pop, there's no one around and I've seen as many as 3 pools appear at once. I usually empty at least 2 of those pools before anyone shows up.
Additionally, I always fish this area. Persistence will guarantee that sooner or later, the RNG will spawn the number of pools in this particular area you need to win the tourney. The week I won it, the pools popped non-stop and it took 19 minutes to win.
And perhaps it's my imagination, but I get a much higher proportion of junk fish when the pool I fish is shared with others.
edit:
And the week I lost it, i was in this same area. Had 40 tastyfish in my pack and found out my hearth still needed 4 minutes. Tried riding to town and made it to the entrance of BB just as the winner was announced.