Updated on 10 July 2017
Batch script to compile and install latest development version of smplayer:

#!/bin/bash
#Install dependencies
sudo apt build-dep smplayer
sudo apt-get install libqt4-dev zlib1g-dev fakeroot build-essential devscripts debhelper g++ mplayer2
echo Checking out sources
mkdir ~/src
cd ~/src
echo Removing old debs...
rm *deb
svn co https://subversion.assembla.com/svn/smplayer/smplayer/trunk/ smplayer
svn co https://subversion.assembla.com/svn/smplayer/smplayer-skins/trunk/ smplayer-skins
svn co https://subversion.assembla.com/svn/smplayer/smplayer-themes/trunk/ smplayer-themes
echo Compiling everything...
cd smplayer
./create_deb.sh
cd ..
cd smplayer-skins
./create_deb.sh
cd ..
cd smplayer-themes
./create_deb.sh
cd ..
echo Installing everything as root
sudo dpkg -i smplayer*deb

Updated on 2 May, 2017
Compile the latest smplayer on Ubuntu(New):
We’ll be building smplayer, smplayer-themes, and smplayer-skins.
Install dependencies:

sudo apt build-dep smplayer
sudo apt-get install libqt4-dev zlib1g-dev fakeroot build-essential devscripts debhelper g++ mplayer2

Get source from the svn and build each package:

mkdir ~/src
cd ~/src
svn co https://subversion.assembla.com/svn/smplayer/smplayer/trunk/ smplayer
cd smplayer
./create_deb.sh
svn co https://subversion.assembla.com/svn/smplayer/smplayer-skins/trunk/ smplayer-skins
cd smplayer-skins
./create_deb.sh
cd ..
svn co https://subversion.assembla.com/svn/smplayer/smplayer-themes/trunk/ smplayer-themes
cd smplayer-themes
./create_deb.sh
cd ..
sudo dpkg -i smplayer*deb

Hurray, we’ve successfully built and installed the latest dev version of smplayer.

To update to latest version:
smplayer will notify new update releases. Once updated, we can compile new one:

svn update
./create_deb.sh
sudo dpkg -i ../smplayer_17.5.0_amd64.deb

Note: I found that on playing, smplayer did not have any sound. I had to change my default audio device to pulse.
Options:Preferences:
Audio>Output driver: pulse

Older post:
First, download the latest smplayer tarball from the official site.

Eg:

wget http://downloads.sourceforge.net/project/smplayer/SMPlayer/16.9.0/smplayer-16.9.0.tar.bz2

Extract it:

tar jxf smplayer*bz2
cd smplayer*

Install essential prerequisites for building:

sudo apt-get install libqt4-dev zlib1g-dev fakeroot build-essential devscripts debhelper g++ mplayer2
sudo apt-get -f install

Now create the .deb package:

./create_deb.sh

Install the package:

sudo dpkg -i ../smplayer_16.9.0_amd64.deb

Alternately download the .deb after installing the prerequisites:

http://sourceforge.net/projects/smplayer/files/Unstable/ubuntu/