To the "symptoms" I'd add an increased need to use the restroom, and a more frequent grinding feeling on your bladder and cervix. Also might notice more lower back pain and increased leg swelling.
If you feel your lower belly, before the baby "drops" you can feel a dip under your belly, before your pubic bone. Afterwards, the head will be at or near the public bone, and you won't have that noticable (as much) "end" of the belly, if that makes any sense.
Since he is your first, you probably will drop a few weeks before labor, but don't stress if you don't. Later pregnancies often the baby doesn't drop until labor begins, or even well into it. My last two were quite high until just before they were born. It was the strangest feeling when they moved down.