The best tip i can give is to backup your projects. Doing this in a file editor can cause problems so what you should really do is go to Assets/Export Package. This created a packed Unity file containing all your data and can be imported into a new project or existing one. If you do import these into an existing project you may have problems with items that are named the same. Currently i rename these items before exporting. If i find a better way i will tell you.
Hide Meta files in Unity
Unity Creates many Meta files inside your project folder this can make things a little messy, So if you would like to hide these files go to Edit/Projects settings/Editor. Under Version Control it says “Mode” and next to this is a drop down box that allows you to choose hidden Meta files.