First of all, Reformed Theology falls within what is considered orthodox teaching which means it does not conflict with essential Biblcal teachings. Of course, Arminian Theology is also considered orthodox. How can that be? Well, orthodoxy primarily refers to a conforming to established doctrines of Christianity...those that are explicitly clear. Other, secondary issues are not as clearly delineated in scripture and are therefore open to some interpretation. Now, on to the common beliefs of Reformed Theology:
Reformed Theology embraces the fundamental common beliefs shared by all Christians (both Protestants and Catholics). Such beliefs would consist of the basic understandings of the nature of God as reveled through nature and (primarily) through scripture.
Secondly, Reformed Theology also affirms all beliefs held by the group called "Evangelicals".
So, what separates Reformed Theology from other Protestant belief systems? It is the understanding of the process of salvation that is unique to Reformed Theology: "Salvation is of the Lord." These beliefs are often remembered by the acrostic T.U.L.I.P. I go into some detail of each of those issues elsewhere.