By prelims I assume you mean the qualifying round at the begining. You need to have the most kills. Kills count as last skill used to kill someone so you can just do that last attack to get a kill. If there is a tie then there is a roll to see who goes forward.
spam killing hte low lvs, id there are 3 lv 70 and 1 lv 42 it would be faster to kill lv 42
they can steal death too, if you are hitting them but the skill that killed them is a opponent skill the score goes to the opponent.
Question do ring outs count in prelims? So if I knock them out would that give me one kill score? And if so what happens if they ring out on their own is the person who got the last hit rewarded?