Here's the list, feel free to add on or argue against these.
1.)
Wearing jean shorts (SECDomination probably sees a lot of these ). You will not get a bid... jean shorts were [marginally] cool about 10 years ago, now they are trashy and redneck.
2.) Being overly cocky, nobody wants a pledge who thinks that they are too good to perform menial tasks, see #7
3.) One word answers. Be conversational, social skills are the most important thing that somebody can possess. The importance of this skill can not be stressed enough.
4.) Don't talk about how much you can drink or how drunk you were the other night unless a really good story comes along with it.
5.) Getting drunktaneous at rush events. Fraternities do not want people with no self control, it becomes a huge risk to pledge someone who can't control themselves.
6.) Do not hook up with girls at rush events unless they are of the highest quality and you have checked to make sure that they are not an active's girlfriend or even an active's
potential girlfriend. Nothing is worse than pissing off a brother or receiving the nickname "free willy" in the first week of pledgeship.
7.) Trying too hard. You do not need to convince the brothers that you are the coolest person ever and they should initiate you on the spot. Be yourself and if you are a fit in that particular organization then you will receive a bid. Have faith in the fraternity, they have been doing this way longer than you.
8.) Name dropping. Goes in line with trying too hard. If you are well connected and friends with a lot of the actives then the brothers will tell the people on bid team this, you don't need to mention it.
9.) Spending less than 45 minutes at a given house. If you want a bid then you have to show the brothers that you're serious. Spend time at the house getting to know people, even if you don't pledge there you can make connections that last for a while. (I get free pizza because of somebody I met in another fraternity during rush, we really hit it off). Meet every brother that you can, the more, the better.
10.) Dress nicely. Avoid hoodies, sandals with socks, etc. Business casual is the best way to go, collared shirt and pants or khaki shorts in warm weather. In the south avoid muscle tees and cargo shorts.
11.) Do not expect a bid just because you're a legacy or know a few guys in the house. Act as if you really want a big and are unsure if you're getting one.
Tips to impress, now that you know what to avoid doing, here are a few pointers that may get you bonus points.
1.) Bring attractive girls with you. This is the absolute best way to get attention and respect from the actives. Find the best looking girls that you know from high school or whatever and bring them with you when you rush.
2.) Go to the post-rush events (if they have them) AND show that you are socially adept. The most important quality in pledges (and arguably in life) is the ability to socialize with everyone (brothers, girls, alumni, parents, etc.)
3.) Have a lot of knowledge and the ability to carry on conversations
.
4.) Use manners. If you are offered food, take it. Hold the door for women and don't swear with any women in earshot, basic things that your mother has been teaching you since you were little.
5.) Mention to whomever is talking to you what in particular you like about their fraternity (i.e. "I notice you won intramurals last year; that's great because I like to be on a winning team and I can play ____")
The few things in italics may not apply to you, the rest of these apply to everybody.