This includes tips for all related derivatives, as coding in these langs often primarily consists of writing the function in the lambda calculus and then compiling it down at the end.
Among others, this includes tips for:
Please post one tip per answer.
We have one tips page already for binary lambda calculus here. However it only has one answer, and it's a tip for the general calculus; not binary specific. We'll have to decide if we want to keep that question open.