In general the selection procedure was as followed:
Days before a transport Gemmeker (the commander) would call in the Jewish "Dienstleiters" in his office at the Kommandantur. These Diestleiters were heads of the different departments of the camp, mostly German and Austrian refugees. Amongst the leaders were Kurt Schlesinger ( the overall head), Rudolf Fried (of the administration), Fritz Spanier (Hospital), en Hans Ottenstein (Antragstelle). Gemmeker declared that he had received a telex message from the Hague (originated in Berlin). On the telex number was mentioned for a specific transport on a specific date. For example 02-02-1942, 1000 prisoners. Auschwitz. The participants then began to fill the transport list. Always first were the punishment cases (S-prisoners'), those taken in hiding or punished for other reasons.
To reach the requested number of the participants then they had to choose from "free" prisoners. When people entered Westerbork they were first taken to the administration. After registration they were taken to the bureau of the Antragstelle. Here newcomers could file a request (in German Antrag) to be put on a Sperre list. This meant that you, for now, were withheld from deportation and you could stay longer in Westerbork. There were more than 15 Sperre-lists: a lsit for Jews who married a new-Jewish partner, a list for Jews influencers at high positions (Barneveld-List), a list for baptized Jewish, for Portuguese Jews, a list for prisoners who were at Westerbrok before July 1942, etc... The requests were checked either in Westerbork or elsewhere, in the Hague or Amsterdam (each list had a different "owner" who decided if your request was correct or incorrect) The Jewish prisoners' who worked at the Antragstelle in Westerbork were (former) lawyers who assisted in the proceedings.
When the transport list were made up by a group of Diestleiders and the S-prisiners were filled in, secondly the prisoners' without a Sperre were put on the list. Then, if there were still room to be filled, the participants looked at the Sperre list. Each of these lists had a different "value" For example the "strongest" list was the first list for people who were in Westerbork before July 1942, the so-called Alte Lagerinsassen. When prisoners had to be chosen from the Sperre-list with the lowest "value" were cancelled, or "platzt" like it was called in Westerbork, to reach the requested number. With each transport this procedure was repeated.
During the meeting with the different Dienstleiders had to come with proposals. The decisions always were mad by Gemmeker (or on of the previous commanders).
A total of 93 train transports took place between 1942 and 1945. 102,000 where deported, these trains departed for Auswitschz, Sosibor, Theresienstadt and Bergen Belsen. When the War was over, only 5400 survived the horrors of the concentration camps.