The personal "a" is not used with DO pronouns, right ?
 

So you say "Golpo a Juan" to say hit Juan

However, what about If Juan has already been mentioned in the preceding sentence. So if I were to refer to juan now as "him", wouldn't it be " lo golpo"? Where does the personal a come into play here?

La "a" personal sólo se añade ante OD explícitos de persona o ante algunos seres animados o personificados, jamás delante de pronombres acusativos.

Un saludo.

My spanish isn't that great yet ... Could you please translate that to English? Thanks.

OK!

The personal "a" is only added before explicit DOs for persons or before some personified living beings, never in front of accusative pronouns.

A pleasure.

What are accusative pronouns?

The ones you used: me/te/lo/la/nos/os/los/las.

Remember: accusative pronouns are equal to dative pronouns, with the exception of lo/la/los/las, which are replaced by "le/les" for the dative case.

Accusatives [for DO, direct objects]:

(Yo) te amo = I love you
(Él) lo mató = He kills him

*Extra*: (Vosotros) sois idiotas = You all are idiot [vosotros form is only used in Spain]

Datives [for ID, indirect objects]:

(Yo) le [OI] doy un regalo [OD] (a ella) = I give a gift [DO] to her [IO]
(Nosotros) les lavamos la cara (a ellos) = We wash their faces.

Note: "We wash their faces" means, literally: (nosotros) lavamos sus caras; but, again, in Spanish we don't say it in this way; it's not incorrect, though...

The order is the same, but in Spanish we usually reduplicate the OI pronoun (dative). For example, the "le" allows to omit "a ella" (to her) and "les", to omit "a ellos" (to them).

In other words: le = to him, to her, to it; les = to them

Better now?

Yes, much better. I just never heard of dative or accusative. But I understand now. Thanks you!