If the twister is far away, that is like 10 miles or so, raise the alarm. Call 911 and tell the dispatcher you would like to report a tornado and give coordinates if possible. Chances are that the NWS already detected it on their radar; they will know exactly where it is. There are classes on how to be a trained spotter and it helps if you take one of these if possible.
If the twister is in your general vicinity, say 5 miles or so from where you are, grab everyone that you can and head immediately to shelter in a basement, a cellar, or other place with as much in between you and the tornado as possible. Then call 911 and report the tornado.
If the twister is in your immediate vicinity aka within the city block IMMEDIATELY TAKE WHATEVER SHELTER YOU CAN FIND. Time is of the essense. Protect your head with your hands and take shelter in anyplace that is not a mobile home, a car, etc. Now is not the time to head outside and whip out your camera phone.
After it passes, be alert for gas leaks and downed power lines, tend to whomever has injuries, and be alert for a possible second tornado.
north
Yes, yes you should, but only as a last resort if no other shelter is available.
If you can see the tornado
I think you should try there are many video showing how to make a tornado in a bottle. Do the experiment and add the marble in there and see what happen.
Take over in a sturdy building, preferably underground. Details of what you should do vary depending on where you are.
Yes. There are hundreds of tornado videos on YouTube.
It is safest to stay underground if you hear/see a tornado.
Quickly put your foot on the gas!
When you see a tornado, go into a secure building or if there are none near you, huddle in a nearby ditch.
You should not be in a mobile home if there is a tornado coming. Mobile homes are very susceptible to tornado damage and should be abandoned for sturdier shelter during a tornado warning.
you will see Cumulonimbus clouds before a tornado which are large, dark, anvil-shaped clouds.
Yes! San Antonio Texas is "at risk", but the last "Tornado Warning" for that area was in March of 2002. See the link below to see the map of Tornado Alley.