There are set of rules for modeling stuff in blender but it varies from model to model. What I mean by this is hard-surface, organic and hybrids of organic and hard-surface all have different approaches and style of model. The general rule for all of them is that you have to analyze and have a good idea how the model looks, functions and behaves in real world and certain situations before you start to model them. There’s also a difference between high poly(film, commercials, etc.) and low poly (video games mostly) but that’s another story, it’s also important to know not only the limitations of your own object that you’re about the model but also the limitations of the budget and hardware when it comes down to films and video games.
I don’t know about toolbox of meshes but here you’ve got something called Hard-Ops wich I assume would be pretty much the same thing. Unfortunately I can’t help you much, fortunately for you you’ve started to get interested in this industry branch right in time when there’s lots of websites with bundle of information and tutorials on 3D modeling. You’ll develop your own workflow and style once you model enough stuff and you really start to realize what 3D modeling is and how it’s supposed to be done and look like.
Sorry, but I can’t help you anymore. I don’t know what else to say, usually, people here and particularly novice want to hear what they wanna hear and that’d be something in the lines of “Ohhh, you’ll become a professional in this industry in 2 weeks just by watching couple of tutorials online, it’s that easy and simple” But sadly this is not the case, you’re gonna have to take a little bit shorter route but still very long non-the less in order to obtain good skills in 3D modeling.
