As a coach, my paradigm may shift slightly based on the form of debate.
Congressional Debate: I'm looking for a few well-constructed arguments. Though I would never ask for evidence in Congress, it earns you points to cite evidence in your speeches. I discourage being a late speaker on a bill unless you have new insights or arguments that weren't addressed previously. Please don't just stand and repeat what many others have said. Keep questions short--the longer they get, the more awkward and confused you sound. Have fun, but joke speeches will drop you to the bottom of my ballot.
Lincoln-Douglas Debate: It's all about the value and criterion (note that a criterion is a measuring tool by which we can see you've achieved your value; it is not a second value). All contentions should tie back to the value and criterion. The winner usually has shown that they either achieve both values better, has the only value that is achieved in either world, or has done sufficient harm to their opponent's case. Though I value logic more in LD than other debate formats, evidence will always enhance my evaluation.
Policy Debate: If it's worth saying, it's worth saying clearly. I do not favor quantity over quality. If I don't have time to write it on my flow sheet, it was never said. In order to win, the Affirmative needs to win all five stock issues; The Negative must win one stock issue (to suggest you could win in any other way is like a basketball player claiming they can win by how good they are at acting like they've been fouled). If the Neg presents a counter-plan, they have conceded the harms and inherency. At this point, you may only attack the plan and show that you solve better. Topicality is still an option if it was presented in the 1NR.
Public Forum: Public Forum is intended to persuade the average person off the street. I will flow the debate, but I will also judge heavily on your communication and ability to clearly explain the arguments on both sides. Overwhelming the "average person" is not the same as persuading them. If you would rather debate rules and pack four minutes with page after page of spewed evidence, I recommend switching over to Policy debate--better yet, change your ways.
Generally: Logic is great; Evidence is great; Logic and Evidence together are AWESOME! Be true to the form of debate you are in--there's a reason there are different events. Respect your opponents. Be ready to debate.