There are certain files created by particular editors, IDEs, operating systems, etc., that do not belong in a repository. But adding system-specific files to the repo's .gitignore is considered a poor practice. This file should only exclude files and directories that are a part of the package that should not be versioned (such as the node_modules directory) as well as files that are generated (and regenerated) as artifacts of a build process.
All other files should be in your own global gitignore file. Create a file called .gitignore in your home directory and add anything you want to ignore. You then need to tell git where your global gitignore file is.
git config --global core.excludesfile ~/.gitignore
git config --global core.excludesfile %USERPROFILE%\.gitignore
This will result in an entry in your .gitconfig that looks like this:
[core]
excludesfile = {path-to-home-dir}/.gitignore
Depending on your OS and tools, the following contains sample of what you might want to include. When you run git status before adding any files to your local repo, check to see if any files don't belong. Add them to your global gitignore as appropriate.
# Node
npm-debug.log
# Mac
.DS_Store
# Windows
Thumbs.db
# WebStorm
.idea/
# vi
*~
# General
log/
*.log
# etc...
If you use WebStorm, you will also need to copy your global gitignore contents to its Ignored Files dialog.
WebStorm | Preferences | Version Control | Ignored Files
File | Settings | Version Control | Ignored Files