The Nielsen/Norman group recently published Checklist for Designing Mobile Input Fields featuring a quick reference of what you should review when designing for mobile.
Text version of checklist of 14 guidelines to follow for mobile input field UX
Should it be there at all
- Is this field absolutely necessary?
- Is the label above it? (Not inside, not below)
- Is the field marked as required (*) or optional?
- Have you removed any placeholder from inside the field?
- Is the field big enough so that most possible field values are visible?
- Is the field visible in both orientations when the keyboard is displayed?
Filling it in for the user
- Do you have any good defaults for this field?
- Any history available?
- Frequently used values?
- Can you use the phone features (camera, GPS, voice, contacts ) to populate it?
- Can you compute it for the user based on other info (e.g., state based on zip code, coupon field)?
- Do you support copy & paste into the field?
- What is the right keyboard for this field?
- Can you make suggestions/autocomplete based on the first letters typed?
- Do not autocorrect for names, addresses and email addresses.
- Do you allow typos or abbreviations?
- Do you allow users to enter it in whatever format they like? (e.g., phone numbers credit cards)
- You can autoformat it for them.