Just a simple front-end technique I thought to be worth sharing:
Form fields can usually do with some more information on what you are supposed to fill in. Examples include valid user name rules, desired date/time format.
On one hand, you want your users to know what they’re supposed to do, as confusing your visitors easily leads to a dramatically decreased conversion rate. On the other hand, you want your forms to look clean and minimal, so your visitors are not bombarded with information. If you show information by every field on your form, it quickly gets cluttered, and that’s exactly what we want to avoid.
Simply hide the elements containing the help text until they are needed. When a user focuses on a field, the relevant information shows up. This may sound like something you would solve with the onfocus and onblur events, but you can actually accomplish it with CSS.