I can't really figure this out myself so I don't think I can really give an example for this question so I'll just ask it and if it's too obscure to really answer say something in the comments and I'll try to add to it. 

So, you guys have really been helping me out explaining は and even が a little in a [previous question](https://japanese.stackexchange.com/questions/28017/when-do-you-mark-%E3%81%8D%E3%82%87%E3%81%86-or-other-similar-relative-time-expressions-with-%E3%81%AF), but now I'm wondering about marking location words with は and が.

I know that usually に and へ usually mark the thing to which you do something and で usually marks where something takes place or by the means of which you do something (by/with). So how do I know when to use a subject/topic marker to mark words like きっさてん、 としょかん、 がっこう etc. that would usually take に, へ, and で. I'm pretty sure I'm overthinking this, but whenever I start a sentence like this がっこう に I'm always wondering if it shouldn't be the topic or subject or something. Forgive the probably somewhat vague question, but I seem to have a lot of problems/questions when it comes to particles.