Chapter 1 We study different classes of compact sets. In particular, the class of convex-compact sets is analyzed in depth. Using these classes of sets, we provide compactness criteria by checking on a quite relaxed set of conditions. In order to ensure that we are really dealing with more general notions, we pay attention to separate the classes introduced. We also provide some stability results of the classes of compact sets used. Some Valdivia and Orihuela theorems are pushed further and an extension of a theorem due to Howard is provided.

Chapter 2 We formulate some results on Banach disks and prove that every convex, relatively convex-compact subset of a locally convex space is contained in a Banach disk. We study in which cases some properties, such as separability and reflexivity, are preserved by passing to the generated Banach space.

Chapter 3 The drop property, the property (alpha) and the condition (beta) are analyzed. A single technique provides short proofs of some results about drop properties on locally convex spaces. It is shown that the quasi-drop property is equivalent to a drop property for countably closed sets. We prove that the drop and quasi-drop properties, the property (alpha) and the condition (beta) are separably determined. We also study the relation between drop property, property (alpha), condition (beta), compactness and reflexivity.