(curtain)
Stage
Directions

(backstage)

wings
USR
up stage right
USC
up stage center
USL
up stage left
wings
off
stage
right
CSR
center stage right
CS
center stage
CSL
center stage left
off
stage
left
wings
DSR
down stage right
DSC
down stage center
DSL
down stage left
wings

(curtain)
audience (front of house)
house left
house center
house right
(back of house)
Enter -- walk on the stage. Example: Emma enters from USR.
Exit -- leave the stage. Example: Mark exits CSL
Cross (X) -- move on stage. Example: Robin x DSC
Counter (cross) -- move on stage in response to someone else's move. Example: Sam counter x DSC, R of Robin.

In your script, notation of your blocking might look like this:
E ent. USR, sees Mark ex. CSL. Rob stand, x DSC, avoiding E. E counter-x DSC, R of Rob. Sam ent. laughing USR, x CS, up from Rob, scare her.

You can also use drawings and stick figures to remember your blocking.