configuring raspbian jessy for easy ssh access

Configure your pi with

sudo raspi-config

Within the menu, do the following
- change the name of your pi, for example 'pi1'
- allow ssh access
- change the password (and remember it)

restart the pi

Now, from some other unix computer, you want to scan the local network for connected devices. This can be done with nmap. You also need to know the IP address of your local network, which is normally 192.168.0 or 192.168.1, but better find it out with either ifconfig or ip addr.
Step by step:
- Install nmap

sudo apt-get install nmap

- find your local networks IP address with either

ip addr

or

ifconfig

joker@joker-Ultrabook:~$ ifconfig
eth0      Link encap:Ethernet  HWaddr e8:03:9a:ee:f4:2b 
          inet addr:192.168.0.131  Bcast:192.168.0.255  Mask:255.255.255.0
 

In this example, my devices IP is 192.168.0.131, so my local networks address is 192.168.0, 131 being my laptops number.

- search the network with nmap:

nmap 192.168.0.0/24

24 is shorthand for subnet mask 255.255.255.0

 As a result, nmap shows you all devices in the network, including your pi. Of course the pi has to be connect to the network via cable or wifi:

Nmap scan report for pi1 (192.168.0.119)
Host is up (0.011s latency).
Not shown: 999 closed ports
PORT   STATE SERVICE
22/tcp open  ssh

Nice, the pi is there, ssh is open, and its correctly named 'pi1'.
You could use its IP address 192.168.0.119 to ssh into it, but using the name is much easier.

ssh pi@pi1