Login:

Normally via SSH i.e. with 

ssh <User>@a.b.c.d where a.b.c.d is the IP of the Switch

Note: There are 2 different types of Switches: "Normal" Switches and Stacks. A Stack is a bundle of switches with an single management-IP. 

Show-Commands

Interfaces

show int status

This gives an short overview of interfaces. It shows if an interface is connected or not or if it is error-disabled (i.e. due to security violation).

CDP

show cdp neighbours <details>

This command allows it to locate connected cisco-devices and displays what kind of device it is:

Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
                  S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone, 
                  D - Remote, C - CVTA, M - Two-port Mac Relay 

Device ID        Local Intrfce     Holdtme    Capability  Platform  Port ID
rtr-58.58.xyz
                 Gig 0/6           135           R T B S  CISCO2911 Gig 0/1/3
dist_xyzxyz
                 Gig 1/1           126              S I   WS-C3750V Gig 1/0/1

Shows that to the actual device are 2 connections active: 

On has the connection beween the local interface GI0/6 and the remote Port 0/1/3. The 2nd Connection is on Interfache Gi1/1 to the remote Interface 1/0/1

Note: The first number describe the "Module" of the Interface. I.e. on that switch there are 24 regular network-ports on "Module" 0 and 4 SFP-Ports on "Module 1".

Running Configuration

show run 

With user-only-rights this might be empty, if rights are high enough this shows the running configuration. This is the active configuration. If everything works and changes was made with "wr" this will go to startup-config. Without write the running-config is reset after a restart.