Anet A8 filament not coming out
From the comments/answers to your main question, the likely culprit is the hobbed wheel not catching the filament firmly enough.



The hobbed wheel I am referring to is the yellowish one at the centre of the picture.  The problem could be due to:


the wheel being of poor quality, with blunt teeth
the wheel being of the wrong diameter (too small)
the spring squeezing the wheel against the filament being too weak
[judging from the picture, I don't own the A8] it could even be that the nut on the lever that is pushed by the spring (top right of the picture) is too far down on the threaded rod, and prevents the lever to move far enough to push effectively.