Meeting with professors in other universities I am a second year PhD student. I am still in the process of finding a research topic. I have a couple research ideas at early stages with two different professors.

I will be in another country for two weeks, for personal reasons. I want to meet with several professors when I am there. First, I believe it is a good opportunity to network. Second, there are a couple professors with very interesting research areas and I can see myself working on one of these areas. 

Since I do not have a concrete research area, is it still a good idea to meet with them? How can I make sure that they will not feel like I wasted their time?
I think face to face meetings to discuss overlapping research interests with a professor from another university is a great way to network and potentially develop a future collaborator, mentor, postdoc advisor, etc.  I think as long as you are clear and upfront in your email requesting a meeting with the person/professor and you also clearly state the topics and research you would like to discuss, then there is little fear that you would be wasting anyones time.  Because the professor would just decline the meeting, if he or she was not interested in the research topic or discussion you wish to have.  I have met with numerous visiting students over the years and many have turned into future postdocs or collaborators.  Hope this helps!! And good luck.