There are times you may need to be absolutely sure a value saved in your dropdown/radio field is one of the provided options.

If you are using custom code to generate a list of posts for selection, you can use this to show the post title or any other info from the post that was selected in your field. After adding this function, you can get any information from that post that you would like.
[25 show_post=post_title]
[25 show_post=post_name] (slug)

Use this code to make sure the date selected in an end date field comes after the date selected in the start date field. For example, if a user selects July 1st, 2015 for the start date, then the end date field will only allow them to select a date after July 1st, 2015. This code will also make sure the start date comes before the end date.