you can set noexec in /etc/fstab for it to be a default as the example below for /tmp. If you need this explained please feel free to ask for an explanation. Once done, just remount or umount then mount the partition. This has further options placed on, also for security reasons.
LABEL=/tmp /tmp ext3 defaults,rw,nosuid,nodev,noexec 1 2
LABEL=/boot /boot ext3 defaults 1 2
memcached is probably easily installable by your package manager, without knowing what distribution you are using however it is hard to tell you the command you need to run.
I doubt your hosting company said to add options like noexec on every partition however, generally it would be /tmp as this helps prevent against rootkit style of attacks, can you confirm what they advised to you? adding noexec to /, /usr and/or /bin could be very problematic.