We have studied low-background techniques in order to improve the background level for Micromegas detectors. These detectors are good candidates for rare event searches thanks to the low mass and the radiopurity of the materials used in the construction; moreover they have good discrimination capabilities. The motivation of these studies is the reduction of the background level in the CAST experiment where three of the four detectors operating currently are Micromegas of the microbulk type. The last result of the experience acquired in low-background techniques has been the reduction of the background level by a factor 4.5 for two detectors in the CAST experiment, corresponding to an improvement of a factor 2 in signal strength.