Woody is right. Pay very close attention to the show rules and make sure to follow them exactly. If you have any questions, there's usually a contact person to call. This is true for local shows and big international shows alike.
Blocking a quilt will always make it hang better and is well worth the time and effort it may take you. It squares up the edges, flattens the surface, and improves the hang greatly. You can wet or dry block, but I get quite good results with a spray bottle of water which is kind of a cross between the two. Good instructions for blocking are here:
http://academyofquilting.com/library...sary/blocking/
Hanging sleeves are another requirement. The entry information will tell you the size (usually 4"), but it's best to make a D sleeve and to put it far enough below the binding that it doesn't show when hung. I do 1" below and it works well. If you make sure the pleat in the sleeve doesn't go above the binding when it's empty, you should be safe. Good instruction are here:
http://wwwbluemoonriver.blogspot.com...lt-sleeve.html
You will also need to label your quilt exactly as specified by the entry instructions. If they say to cover your label, do that too. If they don't tell you how to cover it, pin (safety pin) a piece of muslin over it in a way that does not flop.
If you are shipping your quilt to a show, the entry info will (should anyway) provide some information on where, when, etc. If they're nice, they'll have some hints for you. I fold mine, usually in thirds, with crumpled bubble wrap in the folds to prevent creases and minimize wrinkles. It all goes in a clear plastic bag with your entry info and into the box. Do not use a garbage bag; it's way to risky. Quilts have actually been thrown out by people who don't bother to look inside to see if it really is garbage inside. All the 'rules' for shipping gift quilts also apply to show quilts. Never ship with styrofoam peanuts or dryer sheets. Good info on shipping is here:
http://www.americanquilter.com/quilt...iew.php?id=113
Just remember the judges are looking for what's right with your quilt, not what's wrong with it. It's a great experience, the feedback is priceless, and we all wish you the very best!
There are several threads here on what judges look for so check those out, too.