Contacting a potential research adviser I wanted to know what the best next step is given my situation.  I have been interested in doing research with a professor, however after the initial response from him about setting up a time to meet he has not responded.  Given it was summer I assumed he was busy with travel and grant proposals.  Upon sending two more emails he did not respond about setting up a specific time.  As such, I went to his office.  He send he would send an email setting up a time.  How long should I wait to hear back with a response?  I understand professors are very busy, however there is a deadline to enroll in research credit.  I am hesitant in sending a "reminder" as I don't wish to annoy him.
If you think you are on the edge of being annoying, then it might be better to wait. But, you don't have to wait passively. See what other, backup options you might have with other professors and start a conversation there. Be a bit tentative with them, of course. 

And, if he is negligent about responding, note that he might also be negligent about giving you the guidance you need. So, other options are worth a look. 

But, it is also possible that he is just a last-minute procrastinator sort of person, so be prepared to spring into action if you get a favorable response.