Preliminary selections for a new band of central and regional officials will be completed by the end of spring.
Sources close to the party's Organisation Department said the process was 'much more stringent' than before.
This year's criteria were loyalty to the party bosses, good track records, age, leadership qualities and 'ability to understand the needs of the entire country'.
In provinces with large ethnic minorities, some posts had been reserved for non-Han cadres.
An informed source said: 'In the past, the Organisation Department had authority to pick officials with the rank of vice-minister or vice-governor.
'Now the Politburo is involved in the selection of even vice-ministers. This is particularly so for important departments such as the State Planning Commission, the Foreign Ministry and security-related units.' It is understood the Organisation Department started sending assessment teams to the provinces in late December to examine the qualities of cadres earmarked for promotion.
The teams included retired ministers and provincial party bosses, as well as party elders. While the appraisal of the bulk of regional candidates has been completed, assessment of candidates for top positions in the central ministries will take place through the spring.
The source said: 'Senior cadres of the Organisation Department and the Politburo will study the recommendations of the assessment teams and come up with their decision in the summer.' The appointments will be formally made in the winter and at the National People's Congress in March next year.
The election of about 2,000 delegates to the critical 15th party congress will be completed before Lunar New Year.
An official in a Beijing ministry said the election of the two delegates allotted to it was 'most democratic'.
'All party members working in the ministry and its subordinate units could nominate colleagues,' said the official.
'The Organisation Department never gave us any instructions. Elections were by secret ballot.' The only guidelines issued were that one of the two delegates had to be younger than 50, and that one delegate should come from ministry headquarters and the other from one of its subsidiaries.
The delegates will approve a new Politburo and Central Committee at the congress in October or early November.