I've been wanting to do this for my own purposes anyway, but since I have a blog now I should use it!
In exploring my gender I've thought a lot about the past and anything that might have been an indicator of what I really was (am!).
The earliest item is my very first best friend (only friend for awhile) - Missy (totally ironic that I now use that name for my drag name). I'm not even sure when we became friends, we were both younger than 5 years old though. She lived down the street from me, so to some extent it was convenience, we were the only people close to each other in age - she had a brother and sister who were both substantially older, I have a brother and sister who are older, but they lined up with other kids in the area who were around their age. Convenience wasn't everything though, we were very close and stayed close friends well into elementary school, even after both of us had met other people and could "travel" to play if we wanted. Our usual play routine involved things that I think would be typically seen as "girls" - basically "playing house" with various Fisher Price toys. I had a G.I. Joe, but it wasn't my choice, I would have preferred a Barbie (she had much better accessories!), and in my hands Joe didn't do the things that he would normally have done (he never went to war). Sadly we did drift apart - it was around the age when it was "wrong" to have friends of the other sex/gender (girls had cooties after all).
I didn't have any close female friends through the rest of elementary school or high school - but I was friendly with more girls than boys (in hindsight I can see that they no doubt saw me as non-threatening, so it was easier to get closer). These weren't good years (for multiple reasons that probably had nothing to do with gender).
After that I started having more female friends, and a wife. We ostensibly divorced when I came out as gay, but I can see things from the time of being married that suggested otherwise. One fairly substantial thing is that when it came to decorating the more "female" touches were generally my suggestion! I like pink, I like it anywhere that it looks good, which is pretty much anywhere (for example, I was very excited when I found that I could make this all pink! Hopefully it doesn't make it hard to read). To put an even finer point on it, we didn't paint our living room pink, we painted it "dusty rose." My choice. I'm sure I tried to keep some check on it, but not with complete success. Later on I would ascribe that to being gay, but now...
Since then I've pretty much always had at least one very close female friend. Again I would have typically said that it was because I'm gay - but I honestly don't know many of my gay friends who routinely have female friends, they tend to stay more to themselves (I'm also not denying the possibility that both sexuality and gender play a role in this).
I'll save the more recent indicators for later