Since there are some concerns about the use of hack such as auto-aim in those "TOURNEY" threads, it would be informative for me to share a couple of simple ways about how you can tell if someone is using it. Feel free to share your learnings about this hack if you have any, so that it can make dueling better.
The two things I will post below is under these conditions: non-dialup connection, fast computer, and the dueling ground isn't contaminated by trap remains, vines
1. Vs a range attacker, try to keep yourself on the same minimap with your opponent at all time. If he/she is using auto-aim, you should see all the attacks going right at you when you are not on the same screen.
2. Vs characters that tele on top of you to attack, it's simple. If they tele on you from off screen, they use autoaim (unless they got a namelock on u when u were on the same screen sometimes earlier. but this is not a smart move on their part since they can't move or do anything if they want to keep that namelock). Some clever ones will try to tele on you from the edge off the screen and claim it on lag. So keep in mind that, with good connection/fast comp, you will always see their first teleport onto your screen.
There are ways to fight auto-aim users, but this is not the right thread, and I don't encourage anyone dueling an autoaim user.