I am using FreeBSD to connect to a juniper switch using console connection.
I have crossover network cable: 1 end in switch and other in my freebsd laptop.
What do I need in freebsd and how do I watch what is going on when I poweron the switch?
A console connection has to physically be made using a console cable to the device using either a special ethernet or serial cable. See if you can do a virtual console connection over ssh or telnet.
This point has not been made clearly enough yet: Serious Networking Equipment often has an RJ-45 console port that is not ethernet at all. You need a cable or adapter with RJ-45 on one end and DB-25 or 9 on the other end. (and on a PC with no serial ports you probably need a USB serial adapter too.)
Here's an example of documentation for a console cable: http://kb.juniper.net/InfoCenter/index?page=content&id=KB13272&actp=RSS
There are many variants, so you have to get specific with the model number to find out for sure what you need.