Acting: We really can't recommend anything that may help, other than some studying or classes.
Sound Quality: We expect lines to be without static while being loud and clear. A good mic and amplifier will certainly help. Recording program and sound graphic will also improve on the quality. A good free program will be Audacity. Higher end programs we recommend are Adobe Audition and CoolEdit.
Efficiency: We may be a pain to request lines in tight deadlines or ask for re-dos and additional lines. So upon taking a role we expect a certain degree of responsibility. We will provide reasonable resources like animation updates and scripts, so please be efficient on delivering the lines.