WP7: Thinking about performance implicitly

It's inevitable as the moon going around the earth - the performance of your Windows Phone 7 app will become an issue during your application development life cycle, hopefully you're using agile practices and therefore this won't happen to late in the process. There is one technique I believe you should always apply to the process and that is 'thinking about performance implicitly'.

So I have 3 tips which help me achieve thinking about performance implicitly.

The emulator is not your friend - You should as others have pointed out always be testing on a device and not the emulator - the emulator is great for spiking and unit testing but not as environment for building an application, it runs at the speed of the host and I haven't yet managed to find a WP7 phone to match the perf of my 4 * Quad Core machine :)

Get the worst device possible - Okay any device running WP7 will have been certified by MS as acceptable, but there are still great differences between them. We all want the latest with the best memory, processor etc but in the long run it's better to test against the lowest common denominator - it will save you time & money in the long term (if you can get hold of 2 devices then even better).
I'm currently using an LG GW910 and to say I don't like the device is an under statement, the responsiveness of the touch screen, the quality of the display and the number of 'white screens' compared to newer devices is noticeable, so if I can get good perf from this device then I know it will be better on newer devices, unless something less inspiring comes to the market that is.

Turn off WIFI support - When testing communication to back end services turn off WIFI, test using 2G\2.5G\3G or GSM EDGE it will give you a more real world experience. If your application works great over these it will fly on WIFI.