Group inputs associated with one function within a background container.
Layout inputs in a logical order. Try to group similar input types to make it easier to fill out.
Display form fields side by side only if they're reasonably related. Don't do it just to fill the space.
Display date range fields side by side (and shorter than other text field types).
Stack radio buttons and checkboxes. Use more space between them if they aren't a group of similar items.

Mark mandatory fields with an *.
Use radio buttons instead of dropdown lists for small finite lists and toggles.
Display a calendar icon in the right of date picker fields. When either the icon or the field is clicked, a calendar picker should appear.
Display a downwards pointing arrow in all dropdown lists, and Select2 dropdown fields.
Include a way for users to access a plain text version of their password in a password field.

Size a text field or a text box so that it's indicative of how much text goes inside of it.

Input type	2/3 column (main content area)	1/3 column (secondary content area)	1/2 column (main content, small screen)	1 column (main & secondary content, small screen)
text field - 'normal'	full, half, or quarter width	full or half width	full or half width	full width
text field - date picker	half width	full width	full width	full width
text field - multi selects	full width	full width	full width	full width
2 text fields - date range	full width	full width	full width	full width
text box	full width	full width	full width	full width
select box ('regular' and select2)	full, half, or quarter width	full or half width	full or half width	full width
checkbox - single	full width	full width	full width	full width
checkbox - list	full width	full width	full width	full width
radio button - list	full width	full width	full width	full width