In data mining, frequent itemset are found using different algorithms like Apriori Algorithm , FP-Tree , etc. So are these the pattern evaluation methods?
You can try Association Rules (apriori for example), Collaborative Filtering (item-based or user-based) or even Clustering.
I don't know what you are trying to do, but if you have a data-set and you need to find the most frequent item-set you should try some of the above techniques.
If you're using R you should explore the arules package for association rules (for example).