Ubuntu walk through
Download the client.
https://github.com/ethereum/mist/releases
Extract it to your Downloads directory
CTRL-ALT-T will open a terminal window
cd /Downloads/Ethereum-Wallet-Linux64-0-8-1/resources/note/geth
Geth is hidden but it is there. Execute geth with the following switches:
./geth --fast --cache=1024 --jitvm --support-dao-fork
If you are supporting the ETC chain then use the switch --oppose-dao-fork
On a rather old AMD64 dual core with 4 gigs of memory and a wireless N connection I was able to download the entire chain from scratch in less than 8 hours.
On the same machine just running the binary ./Ethereum-Wallet took 3 days.
When the chain downloads fully you can you can open a new terminal and return to /Downloads/Ethereum-Wallet-Linux64-0-8-1 and run ./Ethereum-Wallet and it will automatically use your already running geth version with the switches.
Parity is lightning fast and that is a great option as well.
One error there is no directory "note"
It should read
cd /Downloads/Ethereum-Wallet-Linux64-0-8-1/resources/node/geth