There may be some regional variations, particularly due to local climate and season.

Normally optional but discouraged. Always worth having one tucked away in a bag, though, just in case.

A jacket is always optional with casual styles.

Might be considered a little conservative or old fashioned.

The smarter the better.

A dark colour often looks more professional especially if it is made out of a nice material.

Collared.

Long sleeves are considered less relaxed than short sleeves.

Clean and well pressed. White is the universally preferred colour, but not essential in a casual environment. Light blue or stripes are also popular.

Avoid double cuffs and cufflinks if you are not wearing a tie.

Or Jumper.

If desired.

Good quality.

Good quality.

Ideally the same colour as your trousers but normally a darker shade. Black will go with most things.

Mid-calf length.

Avoid patterns, logos, and images.

Black is safest.

Leather.

If weather requires.

The smarter the better.

A dark colour often looks more professional especially if it is made out of a nice material.

A wedding or engagement ring is always allowed.