I just had a review asking for …Verb+ておく in the casual form (“let’s do something in advance”), the solution being …Verb+ておこう.
There is such an example in grammar point 162, but I couldn’t find anything about this volitional, casual form in general. I only know the polite volitional form with …ましょう.
Can someone please tell me where to find the volitional casual form for all verb types? (I am using Tae Kim.)