for temporary situations existing for a period at the present time:
• I'm staying with a friend at the moment.
• She's working for and insurance company nowadays.
• Just now I wait to do my military service.
• Just now I am waiting to do my military service.

for situations which are changing during the present time:
• The weather's getting hotter and hotter.

for actions, or repeated actions or habits, occurring at the momenet of speaking:
• I am using John's mobile phone because I left mine at home.
• You're eating too fast.