I'm a little confused here, since the advice for imperatives above is somewhat contradictory. Is it "Usted expliqueme" or is it "Usted explicame" (and by extension it it "Tu explicame" or is it "Tu explicasme")? Iago refers to the placement of the object pronoun (the "me" is not a subject pronoun) but leaves the verb conjugation the same as what is used in the declarative form, whereas hesolomon refers to a different conjugation for the verb without commenting on the placement of the object pronoun.
Yes, there is a difference in conjugation as well. My original comment is correct on the conjugations, and if you want to know more general rules, here are two websites that might help. Formal (Usted/es) Commands: http://www.studyspanish.com/verbs/lessons/formcomm.htm
Informal (Tú) Commands: http://www.studyspanish.com/verbs/lessons/informcomm.htm
Thanks, I think I got the pronoun part OK (about being attached at the end, instead of fronted, if the sentence is imperative). Do you mean that "explica" with "usted" and "me" (and "explicas" with "tu and "me") would have to be the declarative "Usted me explica" (and "Tu me explicas")? In other words, is the difference between the declarative and the imperative not only found in where the object pronoun goes, but is also reflected in the verb conjugation?