Reddit mentions of Horizons, 5th Edition (World Languages)

The best thing you could possibly do would be to read the book "Fluent Forever" by Gabriel Wyner. It is a short read - but get it and finish it within the next week.

Then, go ahead and buy the French textbook you will be using next semester. You can usually look this up on your university website. If you really can't find it, I suggest buying a used copy of this for like 5 dollars on Amazon: https://www.amazon.com/Horizons-World-Languages-Joan-Manley/dp/0495912492/ref=sr_1_2?ie=UTF8&qid=1500038046&sr=8-2&keywords=horizons+french

It is what my university uses and is pretty popular. I thought it was a decent intro level book.

Next, download Anki. Usually textbooks have vocab blocks or lists in each chapter. Input ALL of that vocab, starting with chapter 1 and moving forward, into Anki using the cards that Gabe talks about in his book. Continue to do this (even if the semester starts) until you input every chapter of the book.

If you start now, you will find that by the time the first test rolls around you won't be wrestling with vocab. This will free you to focus on the grammar, as well as speaking and writing.

The people who do poorly at a foreign language in college are the ones cramming the vocab lists the night before the test - you need to have that stuff down before the test is even on the horizon.

Once the semester starts, input the example sentences of the book into Anki (also as Gabe suggests) to start memorizing that grammar too. Anything you struggle with in class, go home that night and input 5 different examples of it in to Anki.

Do Anki every single day. Don't skip one. This alone will put you at the head of your class - and you will have a month head start!

EDIT: There are other resources to use if you want more, but since you will have classes available, I think it is best to do as I say above and focus on the class materials. Doing Anki alone with a university class will make French seem easy since you will have everything memorized so quickly. Enjoy it. Have some fun. Seek out other reading materials to get ahead - the /r/languagelearning sidebar has plenty, or browse my comment history for a lot of suggestions.