To compile  Hadoop Mapreduce next following, do the following:

Step 1) Install dependencies for yarn

See http://svn.apache.org/repos/asf/hadoop/common/trunk/hadoop-mapreduce-porject/hadoop-yarn/README
Make sure protbuf library is in your library path or set: export LD_LIBRARY_PATH=/usr/local/lib

Step 2) Checkout

svn checkout http://svn.apache.org/repos/asf/hadoop/common/trunk

Step 3) Build

Go to common directory - choose your regular common build command. For example:

export MAVEN_OPTS=-Xmx512m
mvn clean package -Pdist -Dtar -DskipTests -Pnative

You can omit -Pnative it you don't want to build native packages.

Step 4) Untar the tarball from hadoop-dist/target/ into a clean and different
directory, say HADOOP_YARN_HOME.

Step 5)
Start hdfs

To run Hadoop Mapreduce next applications: 

Step 6) export the following variables to where you have things installed:
You probably want to export these in hadoop-env.sh and yarn-env.sh also.

export HADOOP_MAPRED_HOME=<mapred loc>
export HADOOP_COMMON_HOME=<common loc>
export HADOOP_HDFS_HOME=<hdfs loc>
export HADOOP_YARN_HOME=directory where you untarred yarn
export HADOOP_CONF_DIR=<conf loc>
export YARN_CONF_DIR=$HADOOP_CONF_DIR

Step 7) Setup config: for running mapreduce applications, which now are in user land, you need to setup nodemanager with the following configuration in your yarn-site.xml before you start the nodemanager.
    <property>
      <name>yarn.nodemanager.aux-services</name>
      <value>mapreduce.shuffle</value>
    </property>

    <property>
      <name>yarn.nodemanager.aux-services.mapreduce.shuffle.class</name>
      <value>org.apache.hadoop.mapred.ShuffleHandler</value>
    </property>

Step 8) Modify mapred-site.xml to use yarn framework
    <property>    
      <name> mapreduce.framework.name</name>
      <value>yarn</value>  
    </property>

Step 9) cd $HADOOP_YARN_HOME

Step 10) sbin/yarn-daemon.sh start resourcemanager

Step 11) sbin/yarn-daemon.sh start nodemanager

Step 12) sbin/mr-jobhistory-daemon.sh start historyserver

Step 13) You are all set, an example on how to run a mapreduce job is:
cd $HADOOP_MAPRED_HOME
ant examples -Dresolvers=internal 
$HADOOP_COMMON_HOME/bin/hadoop jar $HADOOP_MAPRED_HOME/build/hadoop-mapreduce-examples-*.jar randomwriter -Dmapreduce.job.user.name=$USER -Dmapreduce.randomwriter.bytespermap=10000 -Ddfs.blocksize=536870912 -Ddfs.block.size=536870912 -libjars $HADOOP_YARN_HOME/modules/hadoop-mapreduce-client-jobclient-*.jar output 

The output on the command line should be almost similar to what you see in the JT/TT setup (Hadoop 0.20/0.21)