strange how the bases change as you age. i think there need be a caveat:
young bases (decide the age for yourself):
1st - acknowledging the other exists in front of your friends
2nd - laughing at the same jokes obnoxiously
3rd - telling people you're "going out"
4th - holding hands
"advanced" teens:
1st - kissing
2nd - touching boobies
3rd - rubbing lower extremities
4th - dry humping
college
1st - getting drunk
4th - waking up
professional
1st - getting number
2nd - getting her to agree to dinner
3rd - spending the wad
4th - she agrees to 2nd date
marriage
1st - she takes out the garbage for you
2nd - you agree to mow the lawn
3rd - you do the recycling together
4th - business time.
just a few examples.