Here are 2 simple tips for Application Express. Watch the short videos for a hands-on tutorial.
1) creating a Shared LOV from a LOV in an item.
http://www.youtube.com/watch?v=oQv9DDcZt4U
This is especially useful if you created an item LOV and discover you want to use it in othet places too.
2) Create a dynamic autocomplete field.
How to create a dynamic autocomplete field.