Open Settings > Store > Automatic Downloads > Apps = On

Anytime you download an app on your iPhone or download an app in the iTunes store on your computer it will also appear on your iPad if it is able to run on the iPad. A couple things to note though:
- You must be using the same Apple ID on both devices or signed into same account in iTunes on your computer
- If you turn automatic downloads on your iPhone, iPad apps will not install on the iPhone of course
- Some apps may not install over 3G, any App over 50MB has to be downloaded over Wi-Fi
For more great iPad tips, follow me on Twitter @icrizzo
