A usage question in Spanish

In general, no.

In Spanish, like in English, you only use words if they convey something unique or for emphasis. So "yo" tends to be used to emphasize, or is used in tenses where the third person and first person are indistinguishable. Past perfect first person (Camine), is distinguishable from past perfect third person (camino and yes, I left off the accents), so you don't need "yo", although you could add it for emphasis.

"Caminé" already says "I walked." The verb form gives you both person (yo) and tense (é = past). So the "yo" isn't wrong per se, but it also isn't necessary.

You can use "yo" to make a sentence stronger, as in a command ("¡Haz lo que te dije yo!") or added to a phrase in a flip, slangy way ("Sabes te quiero yo.") It's mostly a matter of style or choice.

HTH

Another thing is that Spanish has the ability to eliminate pronouns and, usually, you will find that the use of pronouns becomes utterly repetitive. Take this sentence:

He walked through the door then opened the fridge. What he saw perplexed and disgusted him, what kind of savage would keep those in a fridge?

If you translate it DIRECTLY:

Él atravesó la puerta y él luego abrió la refrigeradora. Lo que él vio lo impresionó, le generó asco, ¿qué clase de salvaje mantendría eso en una refrigeradora?

It sounds a bit annoying, so you can do this:

Él abrió atravesó la puerta y abrió la refrigeradora. Sintió asombro y asco, ¿que clase de salvaje mantendría eso en la refrigeradora?


Hope that helps.