Following iPad\'s announcement and its SDK (iPhone SDK 3.2), porting apps to iPad becomes an important issue. What guidelines I should follow in my iPhone apps to ensure I can p
Judging by what has been said, absolutely nothing. You will have to adapt to the new screen size and better hardware all together, if you want to take advantage of the features that the improved device offers. The lack of a 3g module is also something to consider if your app(s) rely on that functionality.
It is far more reasonable to expect users to input text (and larger amounts of it) than with a non-iPad device.
If you've been using IB and setting the resize behaviors of elements properly, and also coding frame coordinates all relative to each other you are half-way to having a UI that can potentially scale to a larger screen.
From the screen shots there are new kinds of action-sheets as well, potentially attached to UI elements instead of floating - if you use overlays today they will probably work about the same but you may want to consider changing placement from the center on larger display.
UPDATE:
Now the event is over, and registered developers can download the SDK - although we cannot talk about specific features here just yet, read through ALL of the documents related to the new OS version as there are a number of things aimed at helping you transition to supporting both platforms. Also before you start using custom libraries for things take a look through the API changes to see what new abilities might be supported that are not today.
Generally speaking, what I said above about IB holds true, and also you should start thinking about how your apps today could use more space to present more information at once instead of being split out over multiple screens. Also if you are doing any projects right now that use images, make sure to initially design the images large enough that you can also use them for higher resolution tablet applications.
Nothing, it appears. Although we don't have the SDK quite yet. It will all existing run iPhone app without an issue, albeit at reduced resolution.
It remains to be seen how much of the existing iPhone SDK is shared with the iPad SDK UI wise.