Be aware that the Altium documentation goes into much more detail than necessary for our purposes. The best way to gauge how much you know or don't know is to start a project.
Getting Started: http://techdocs.altium.com/display/ADOH/Getting+Started+with+Altium+Designer
Schematic Capture
When designing a printed circuit board (PCB), schematic capture occurs after deciding what functions the circuit must perform and selecting proper components to implement those functions. Schematic capture refers to the process of drawing out the circuit using symbols to represent each component.
Schematic Editing Essentials - http://techdocs.altium.com/display/ADOH/Schematic+Editing+Essentials
Design Objects - http://techdocs.altium.com/display/ADOH/Schematic+Editing+Essentials#SchematicEditingEssentials-PlacingDesignObjects
Any visible component displayed in the Schematic Editor. There are 2 types of Design Objects, Graphical and Electrical. They can be placed with LMB and rotated with Spacebar
Graphical Objects - Lines, arcs, text, boxes
Electrical Objects - Parts 
, wires 
, buses, ports
For ease of navigation and object placement, interactive grids will lock cursors to their vertices. This is an important feature and should be properly configured to prevent misaligned components or missed electrical connections. To edit these grids, go to Tools >> Schematic Preferences.
Visible Grids - Adds a non-interactive visible grid to the schematic
Snap Grids - Locks the cursor to its vertices when placing/moving design objects
Electrical Grids - Ignores the snap grid and locks the cursor to its vertices when making electrical connections between design objects. Electrical Grids should be slightly smaller than Snap Grids.
Designators and Annotation - http://techdocs.altium.com/display/ADOH/Understanding+Design+Annotation
Annotation is the process of uniquely identifying every component using designators. Each component designator can also be annotated manually, but
Printed Circuit Board (PCB) Layout
PCB layout generally consists of 5 steps: determining the layer stack, placing each component, electrically connecting all components with traces or polygons, design rule checking, and gerber creation.
The PCB Editor - http://techdocs.altium.com/display/ADRR/PCB_Edtr-PCBEditor((PCB+Editor))_AD
Moving Around - http://techdocs.altium.com/display/ADRR/PCB_Edtr-PCBEditor((PCB+Editor))_AD#PCBEditor-Panning
Design Rules and PCB Manufacturing - http://techdocs.altium.com/display/ADRR/PCB((Design+Rules+Reference))
Design rules are what defines the constraints (rules) for every aspect of the PCB. These rules are mostly distances between objects and will be discussed in more detail here. The design rules must follow the manufacturer's specifications and tolerances in order for the PCB to be made with as few errors as possible. The Design Rule Checking (DRC) tool is an automated way to check if your PCB has violated any of the design rules, and should be used throughout the PCB layout process, most importantly before gerber creation.
Libraries
Schematic/PCB Synchronization
Guides