I remember talking to DD's pediatrician at her 16 mo. checkup because she was only saying a few understandable words at that point. In the next couple months her speech took off and at 2 her speech was clearly very advanced and she was talking in 20 word complex sentences with no articulation difficulties. She would rattle on to complete strangers, and call them "honey". She used the word "honey" in every other sentence. People thought she was a couple years older than she was. She was also able to count up to 40 or 50 at age 2 with one-to-one correspondence. She started reading at 4 and was fluent by the time she started K.
We did see a few things when she was a baby--for instance she was very socially adept and would do things like fake sneeze at 9 months old just to get attention. She wanted people to look at her and say "bless you." But in terms of gross/fine motor skills and speech at age 1, she seemed pretty average. We didn't really start to see that she was advanced until she was 2.
I always thought of her as being verbally advanced and very articulate, so I was kind of surprised by her IQ tests a week ago--she scored 153 for perceptual reasoning and 135 for verbal comprehension. I was totally not expecting a PR score that high--I've always thought it was my DS who was advanced in that area, with his photographic type memory.

DS scores in the 99th percentile for his GAI now at age 6, but had some huge delays. He was actually advanced for motor skills as an infant and was walking well by his first birthday. He said his first words around his first birthday. He was able to climb out of his crib and walk up and down steps. But then at around 1.5 speech/motor skill development pretty much stopped. We now know he has developmental coordination disorder. But even as a toddler he was clearly intelligent. He was obsessed with figuring out how things worked. At age 1 he was fascinated by high chair and carseat buckles and would snap and unsnap them while examining the mechanisms. He loved puzzles and shape sorters. When he was 2 or 3 I caught him trying to take my computer apart. He had a screwdriver and electrical cords in his hands and said he was fixing my computer. He was very good with a computer and knew how to operate Windows and the mouse at 2.5 or 3. Around his 4th birthday I figured out he could read by sounding out words, and he was fluent w/ reading by his 5th birthday even though he hardly ever worked on it.
Now at age 6 he scores in the high average range for verbal ability but above 140 for non-verbal ability. With him, I think there has been a lot of uneven brain maturation and he seems much like one of the kids described in the book "The Einstein Syndrome".
It's hard to tell with preschool age kids what is really going on but both of my kids had signs of advanced abilities, even as toddlers. With DS things were esp. confusing because he had advanced abilities mixed with delays. Turns out he's 2e.