Forget to do OR Forget doing?????

forget + to do=to not do an action you should do

forget+doing=to not recall an action

first ex:
Don't forget to meet her at ten this morning.(you should meet her at ten.....).
I'll never forget meeting her for the first time.(I'll never forget when I met her...).

second ex:
I forgot to lock the door(I didn't lock the door because I forgot).
I forgot locking the door.( I locked the door.Then I forgot about it.I don't remember locking the door).