Journals have impact factor. Google how to know a journal impact factor..plenty information is available.
Nothing well defined at all. We guess that. Here are some tips:
- Ask your supervisor, if his work known to be high quality.
- Typically stars of a field submit only in top tier conferences. If you know 1 star, you knew them.
- Also...If you have 1 top tier conference paper, it will reference top tier conferences...following references can determine them.
- One more way....Google them...find many pages describing top ones...intersect them..pick around 3-5 top ones.
For vision field, here is what I understood through experience:
Last update: 10 Jan, 2015