Etiquette

What is the proper way to respond to a blog for the first time? Should you identify yourself? Let the writer know who you are so they know a bit about you...or just start into what you want to say?
Also, how do you let someone know that you've been thinking about them, but it has been years since the last contact? Here lately I've been dreaming about people I went to high school with and with the ease of the internet, have been able to look them up. Some that I was pretty good friends with, I e-mailed just to say hi, but some...I didn't really know if it would be weird or not. I mean, can you really just say hi to someone that you 'dated' in 10th grade, then were friends with afterward?
I guess this boils down to the can you be friends with anyone you dated in the past category of life. I have several friends that I dated in the past, but the breakup was mutual and the transition from friend to boyfriend to friend again was not that hard. Then I have some that we were friends then dated then we broke up from distance--going off to college, moving, going home for the summer, etc. The last thing in our relationship history was a breakup. It's not like I haven't moved on, and I'm sure they have too, but can I just pop up into their blog or inbox and say hi without looking like a stalker?
One funny that has come of this has been finding out that a friend of mine from high school named his daughter after me. He didn't tell me this, but was telling me about his wife and kids and just happened to write "...and Genniver just turned 9..." So maybe I have nothing to worry about.