First of all, you need to get an object with a small point. Make sure that the object is slim and has sharp nose. A paper clip is probably the best thing to use in this regard. Furthermore, one can also use pins or needles without any hesitation.
Make sure the pin does not injure your fingers. Hold the pin with your thumb and index finger, with the sharp nose pointing towards the computer.
A pin is the only thing you need. After getting the equipment, you need to make a very simple move. Find the hole on the DVD-ROM. Mostly, you will find this little hold near the face of the drive or door.
A few players have this hole right next to the eject button. The little button inside the hole is directly connected to the player, and will make the door come out.
Gently insert the pin into the hole, applying slight pressure. This will eventually release the mechanism holding the door closed. Here you need to be very careful. Applying any extra pressure could make things very tricky for you.
You can either damage the machine or injure your own hands. Therefore, be very gentle. The best way is to apply pressure slowly, and increase it gradually until the door opens.
If the trick is not working, you should try some other object. The pin you are using may not hit the exact point inside the hole. Once the door opens, retrieve your disk and push it back.
You need to understand that this procedure should be used only in emergency situation. Your player will be damaged, if you are not practising this on constant basis.