Performance Appraisal process


I work in an IT Services company and I am currently designing performance management process in my organisation. Any guidelines regarding the frequency of performance evaluation and some guidelines to proceed with smooth implementation of this process. According to my research, Appraisal period to be Jan to Dec, bi-annual appraisals to be only performance evaluation based and during annual appraisal, the salary increments & promotions to be done. Please suggest if this is ok. Also wanted to check the eligibility of new joiners for the annual appraisal. How much duration to be considered for them to be eligible for the appraisal process (increment / promotion).