What is the best age for starting to dance and is 18 too late??
What are the best things that I can do for having good dance results?
Is someone interested in online teaching me from time to time, or just discussing some techniques in order to help me learn?

There is no good or bad time to start. Just do it. However online you can use video clips as available here or text based teaching but none of these tools can see your body's movements or your reactions to the suggestions. For that you will need to find a teacher as you start then after a year or two get a partner and coach which will only be available where you are. Do you want good competiton results or good social results or good showcase results all will need to be explored with your teacher as they also have the pulse on what is appropriate for your area. An example is: a showcase here is often expressed for an audience on one or three sides which affect choreography. What is the venue you are dancing there are many details that can only be answered in your area.

jo£

i think that dancing is for all ages and i don't think that starting at age 18 is too late. i'm not a teacher or anything i'm actually in your shoes i'm 18 and i just started dancing to. i can't really tell you where to go for help though i'm sorry. anyway good luck with your dancing.
Sabrina