Always send your best quality recordings.
Labels have no sympathy for amateur recordings. Cheap sounding material gets shut down instantly. If what you're trying to sell or market sounds like a bedroom recording then that’s where it will stay. Quality recordings get respect. You want to have your demo sounding as close to a finished product as possible, therefore, always send mastered songs. This will validate your seriousness and lets the A&R person know that you're committed to your music. You wont get a second chance to deliver your first impression.

Three or four songs on CD is considered standard.
In addition, song clips or snippets are a good idea as well. Remember, you're just giving a demonstration. If the label wants more, let them ask you for more.

Present yourself professionally.
To be taken seriously, you must show that you can present yourself well. Labels like people who handle themselves in a businesslike manner.

Keep it short and simple.
Reps simply aren't looking for potential. All the A&R person cares about is hearing a hit when he or she pushes the play button. Put your best tracks first. If you can demonstrate the ability to write hit songs that can get radio airplay, they'll hear it. Quality and catchy songs will probably get you the most favorable response.

Include information about yourself.
Give them something to look over while listening to your demo (example: press releases, logo, photos, newspaper/magazine articles, performances info, website reviews, and bio). Remember record companies are in it for the money. If record labels find out that you are already creating a regional buzz on your own, and have sold just 3,000 CDs on your own, then you have their full attention. Also, be sure to include the name, address, and phone number and email of the contact person.

Copyright your songs!
Protect your songs before sending them. Telephone the copyright office in Washington, (202) 707-5959 to obtain general information or if you have questions relating to copyright registration visit their website at copyright.gov

Thank the company for its time and consideration.
Let them know you are appreciative of the time they've invested in you. At least they will be impressed by the fact that you are considerate.

What to do after you've sent your demo.
Dozens of people submit recordings weekly, and it takes time to listen through these.  The hardest part is the wait.  Allow at least 2 weeks before you call to find out if they've had a chance to listen. If they haven't, politely try and get an idea when they will be getting back to you. Be patient!