I think the reason why people have trouble getting signed is... you prolly suck. Alot of people feed off of complements that people give them. Alot of these people dont even know a thing about music. Look for the complements from real musicians. Try and locate critics to check out your stuff.
Another thing, is I dont agree with "AKE" about going to studios to have them make your stuff. Sure if you have a ton of money to give to a studio to make your demo.. good!. I'm friends with people from a few central new york studios, and i know that if you dont have alot of money, they arn't going to spend alot of time on making your mix the way you want it. As a future Recording Engineer, I've been recording since I was about 12.
If someone tries to record a demo by themselves that dont know a think about sound, then yes, go to a studio. But it you at least know about effects, and eq'ing, and playing, then thats good.
Alot of labels are looking to see if you are a good band, the Mix is a big deal, but it wont jepordize you if its not perfect.
Mainly try to figure out if your good first. And try to do something that is unique, but not weird.