There's different variations of this. Here's what I heard.

"baseball" for what's being done to the MALE body.

1st - Kissing of some sort (anywhere from a peck to a french kiss. Depends on whose variation.)
2nd - Touching of your special area (either over or under the clothes. Depends on the variation.)
3rd - Oral
homerun - sex

"baseball" for what's being done to the FEMALE body
1st - kissing of some sort
2nd - Could be touching the breasts over or under the body, could be touching the breasts and touching the vagina over/under the body. Depends on whose variation.
3rd - Could be touching the vagina over/under (if 2nd is just touching the boobs) or oral if 2nd is touching EVERYTHING. Or basically anything else that's NOT sex.
Homerun - sex.

See how confusing this 'system' can be?

Alexi