Tell me about a particularly memorable appointment with your friends.

I met my friends at a bar.
It was a halloween day, so my friends invited to me. (day here is okay if you are refering to the daytime of halloween... as the opposite would be halloween night).
We wore a halloween cloth and hat.
All of the people looked so funny. (To be concise, 'Everyone' is a better word.) 
We all drank beer, and danced together,
and we played pocketball too.  (When listing items, each item is separated with a comma (,) and only the last item uses the 'and' before it.) (Optional: 'too' or 'as well')
It was a lot of fun. that was my first halloween day with my friends.
I can't forget that day. (This is okay if you are telling yourself you can not forget this day. Most people would say: 'I will never forget that day' or 'I won't forget that day' and so on.) 

Tell me about a particularly memorable appointment with your friends.

I met my friends at a bar
It was a halloween day, so my friends invited to me. (It was Halloween, so my friends invited me.)
We wore a halloween cloth and hat
All of the people looked so funny
We all drank beer and danced together
and we played pocketball too (You could combine these two: We all drank beer, and danced together, and we played pocketball too.)
It was a lot of fun. that was my first halloween day with my friends
I can't forget that day (I won't ever forget that day!)

Good job!  The writing in Blue is just another way you could say it!