Install on Ubuntu and Debian:  apt-get install mercurial

The actual version information: hg version
Create a new repository in the given directory: hg help init
hg init [-e CMD] [--remotecmd CMD] [DEST]

Making a local copy of a repository: hg clone <directory>

Through history: hg log or glog
Viewing specific revisions use the -r (or --rev) option
hg log -r 024584ws345
hg log -r q272e0d5w32 -r 0272e0d5w324

More detailed information add -v (or --verbose) option
To see content of a change add the -p (or --patch) option

To display the change set: hg tip -vp
pull the changes: hg in, hg pull
update the working copy: hg up

merging the changes

incoming change: hg in -v
outgoing change: hg out -v
hg merge -r default (tip)