Off to KUL on BA33 this Friday, and just wondering if there are any "wish I'd known..." tips or tricks for a smooth arrival and departure ?

For example, when I went to AUH last year, I wish I'd known how slowly the immigration queue moves - then I would have filled in my form while shuffling forward rather than winding up stuck for 2 hour behind 100+ savvier pax

I read that KUL immigration waits can be pretty long and the hall rather chaotic.

Grateful for any information from people's experience !