In case you haven't had a chance to check it out, I highly recommend the IHS Excerpts page. Horn players worldwide are grateful to Daren Robbins, who created this compilation of horn excerpts. There are many wonderful excerpt books out there, some more comprehensive or more in-depth, but the great feature of this excerpt list is the accompanying collection of audio recordings. Horn players can easily see and practice the excerpts, and can also listen to the excerpts--in full context. There are several different audio recordings for each excerpt, allowing listeners to compare and contrast a multitude of styles, tempi, horn sound, etc.
If you don't know where to begin, I recommend listening to and learning Tchaikovsky Symphony No. 5.
Check out the horn excerpts now: www.hornsociety.org/hornexcerpts-org
Often, students and their families have a string break on their French horn, making it impossible to use the horn properly.
Although you can take it to a local music shop to be repaired, you may want to consider repairing it yourself. It takes a bit of time the first time you do it (I would plan on about 30-60 minutes if you've never done it before). You also need string and a few tools.
However, once you've learned how to do it and have all the tools and supplies you need, it will take you only 5-10 minutes in the future, and will save you a trip to the repair shop.
This youtube video posted by a band director provides a great tutorial on how to do the necessary repair. You can buy the string you need for the repair online, including at Amazon.
Horn teacher and performer