So how will I change my android’s default app download location from device memory to SD card? I have seen this questions asked in many android forums. There is no straight forward way of doing this if you are not rooted. If you are rooted, you can use the App2SD app from android marketplace to accomplish this. But if you have an unrooted phone, It requires you to connect your android device to the computer. Here is a good write up regarding the same. http://androinica.com/2010/08/how-to-install-apps-to-the-sd-card-by-default-on-android-2-2-froyo. The process is a bit time consuming, but it is really worth for people who want to make SD card as the default download location for android.
But be warned that some of the apps when moved to SD card will stop working. Most of the new apps does not have this issue. But mainly desktop apps and theme apps and some alarm apps have this problem.
How to move android apps to SD card
If you ask me, Move all your apps (except the desktop apps) to SD Card. You can do this by going to settings ==> applications ==> manage applications. Tap the “All” option in top. Now tap the menu hardware button (left of the home hardware key) and select sort by size. Now you will be able to see all the apps with biggest size on top. click the biggest one and there will be an option called “move to SD card”. click that and in a few seconds, the app will be moved to sd card. You can bring it back to device memory by following the same process. This is the most effective way of doing things. Changing the default location can sometimes result in unforeseen issues.