How do I change the default quick dial telephone number?

Contacto by default selects the mobile phone as the quick dial number for a contact. You can change this by double-tapping on a contact, enter into edit mode (top right button), and select (single tap) a phone number, email or html page. A checkmark will appear next to the new default number.

How do I delete a group (or contact)?

Long tap on the group or contact icon, press on the 'x' button that appears (at top-left of the icon) and confirm. Alternatively, you may double tap on this group (or contact), enter edit mode (top-right button) and scroll down to the delete option.

How do I rearrange my icons (groups or contacts)?

Tap and hold anywhere on the group view and you will enter rearrange mode. Hold and move your finger on an icon to exchange its position with another one. Hold the icon and move it on the right or left screen border to move the icon across multiple screens. Yes, it could be fun!

Is there a way to email every contact in a group all at once?

Double tap on the particular group icon to enter the group properties, then tap "Email To Group Contacts".