1. INSALL: APC v 3.0.12

wget http://pecl.php.net/get/APC-3.0.12.tgz
tar xvzf APC-3.0.12.tgz
cd APC-3.0.12
phpize
./configure --enable-apc-mmap --with-apxs --with-php-config=/usr/bin/php-config
make
make install

2. EDIT: /etc/php.ini
extension=apc.so
apc.enabled=1
apc.shm_segments=1
apc.optimization=0
apc.shm_size=128
apc.ttl=7200
apc.user_ttl=7200
apc.num_files_hint=1024
apc.mmap_file_mask=/tmp/apc.XXXXXX
apc.enable_cli=1

3. RESTART:

apachectl configtest
apachectl restart

4. TEST:

make sure phpInfo shows php 5.1.4 apc is listed