  This paper is the first part of the manuscript written in April 2012 for my
academic Accreditation to supervise research. It offers a review of the double
beta experimental techniques. My purpose is to detail, for each technique, the
different origins of background, how they can be identified, and how they can
be reduced. Advantages and limitations are discussed. This review is organized
as follows. First, the question of the possible Majorana nature for the
neutrino is presented and the physic of neutrinoless double beta decay is
summarized. Then I begin by presenting the tracko-calo NEMO-3 and SuperNEMO
experiments. I've worked on these two experiments since 15 years. So it was
natural to start with them with a relatively more exhaustive description. I
will then present the germanium technique. I will then review the bolometer
technique. I will describe in detail the recent progress in scintillating
bolometers because I think that it is one of the most promising techniques.
Finally I will review the large liquid scintillator detectors and Xenon TPC.
The last chapter offers a summary of the different techniques and projects.
