This is what I do to get excellent hash rates.
I use 11.12 CCC with 2.5 SDK
Download your appropriate 2.5 SDK, what ever fits your operating system.http://developer.amd.com/sdks/AMDAPPSDK/downloads/pages/AMDAPPSDKDownloadArchive.aspx
you can find 11.12 CCC driver anywhere on the net, sdk is kinda harder to find so I linked it
It's excellent that others posted some other miners but it's up to you.
Get latest GUIMiner https://bitcointalk.org/?topic=3878.0
download it, install it. Select File, new miner, new opencl miner.
In the new tab, select the pool you want to mine at from the drop down list, fill out your login info and pop
-v -w128 -f 7
in to the flag area, you can adjust the -f flag up and down, I found 7 best suits my processor, if you are on your desktop using the mining card set -f to 25. It's the aggression.
If you are like me, you will find this the easiest way to gain 400 mh/s.
I've got my card set like so using sapphire trixx
1000 Core/350 memory/1.125voltage/75% fan speed. if you see temps raise any higher than 74c-75c, shutdown the miner, reboot. Got for default voltage with the highest core setting as possible without crashing, maybe 915Core. Go from there.