Improved mean-field-like renormalisation group approach for Z(q) symmetric spin models

Various modifications of the mean-field renormalisation group method are analysed to study the convergence of the critical coupling and critical exponents to their exact values as the cluster size increases. Appropriate choice of the length scaling factor o r of the scaling quantity can give appreciable improvement over the concentional procedure for short clusters. The best Lalues are achieved when both the bulk and surface critical behaviour a re explicitly taken into account.