This first one is for intermediate and advanced: There is a great series of books called Linguality. They're out of print I think, but you can find them on Amazon. They are shortish french novels with a page by page glossary of terms. I found these books extremely helpful, and also the novels themselves are entertaining. Otherwise, I keep a long list of phrases both on paper and on my phone and I try to use or practice several each day. I also listen to the Coffeebreak French podcast in the car and watch Street French on YouTube for tips on colloquial conversation and slang words.