Learn Farsi: باید برای او تله بگذاریم و دستگیرش کنیم. - We must set a trap for him and arrest him.

Both are grammatically correct, but using the pronominal enclitic ـش (-ash, meaning "him") is very common and natural in Farsi. Instead of using the independent pronoun او (u) with the object marker را (râ), Farsi speakers frequently attach the enclitic directly to the nominal/adjective part (دستگیر) of the compound verb to make the sentence flow better.

Could I attach the ـش enclitic to the very end of the verb instead, like دستگیر کنیمش?

Yes. In casual spoken Farsi, you will often hear the enclitic attached to the auxiliary verb (دستگیر کنیمش). However, attaching it to the non-verbal component (دستگیرش کنیم) is slightly more standard and works perfectly in both formal writing and everyday speech.

Why does بگذاریم get the subjunctive بـ prefix, but کنیم does not?

The word باید (must) forces the verbs that follow it into the subjunctive mood. With simple verbs like گذاشتن, we add the بـ prefix to make بگذاریم. With compound verbs using کردن, the بـ is frequently dropped (so کنیم instead of بکنیم). Dropping it is especially common when it is the second verb in a sequence joined by و (and).

What is the literal translation of the phrase تله بگذاریم?