For those of us that only have young children, and no concrete *proof* of GT ability -with testing being unfeasible at this age, you're primarily left with unqualified observation/instinct by default - there are very few sources of useful information, other than sites like this.
I regularly follow this wonderful board not because I want to know if my children are GT (I guess I wouldn't be here if I didn't already think it), but to try and understand them better and to help make meaningful decisions regarding their future. This site also allows me to feel my family is 'normal', despite my intense children's far-from-typical behavior.
That being said, I would like to weigh-in on the early speech/gross motor skills topic. My two children are both physically advanced for their respective ages (DS3 is currently perfecting a sequential running/dribbling/hoop shot with the basketball, and DD18mos can now ride a two-wheel bike with training wheels. DD spoke 2+ word sentences from 6mos and is now at 5+ word sentences. She can sing both words and melody for more songs than I can count (not just nursery rhymes either). DS was a later talker (around 2yrs) but now speaks in paragraphs with advanced vocabulary. These particular facts alone however, are not the reason that I believe my children are GT (although they are probably the biggest conversation starter's with strangers!). It's what DD and DS are talking about or trying to do, that is more telling, IMHO. The other key factor here is that across the board, the gap between their abilities and normal development milestones widens almost daily. I guess in relation to my two, I feel this is something like the 'all children even out in reading by 3rd grade'... It'll be interesting to know if what we have seen in these younger years correlates down the track. Maybe that's what you're wondering too, Faithhopelove19?