title: POS UI design & development: what should be included & avoided?
body: <p>I'm having to design &amp; develop UI for a Point of Sale (POS) system. 
  There are obvious features that need to be included, like product selection &amp; quantity, payment method, tender amount, user login (as many users will use one terminal), etc.</p>
  
  <p>My question is related more towards the UI design aspect of developing this system. 
  How should UI features/controls be positioned, sized? 
  Is there a preferred layout? 
  Are their colours I should be avoiding?</p>
  
  <p>If you know of any resources to guide me, that would also help.</p>
  
  <p>The reason this is critical to me as I am aware of the pressurized environment in which POS systems are used &amp; I want to make the process as (i) quick, (ii) simple to use and (iii) result driven as possible for the user to service customers.</p>
  
  <p>All answers, info &amp; suggestions welcome.
  Thanks.</p>
  
  <p>P.s. If you could mention the "playoff" between controls that would also be appreciated (i.e. if touch screen a keypad control is provided, but if also supporting keyboard &amp; mouse input how do you manage the keypad &amp; UI space effectively?)</p>