Here’s an article from Lifehacker that boils down the essential points for whether it is a good time to refinance.
I think some points that people may overlook are thinking about how long you’ve had your current loan, and not just the payment amount but the amount which is going to principal. In traditional mortgages you pay mostly interest at the beginning of the loan, so it may not make sense if you’re just going to get another long term mortgage. It makes sense to seriously look at shortening the length of your note.
If you’d like assistance looking over the different scenarios of a refinance, please don’t hesitate to call.