Assuming you have metal braces:
You should brush your teeth at least four times a day, and floss at least once. It's important to be gentle when brushing and flossing around your braces. You can use an interdental brush to help get in between the wires and brackets of your braces. You should also avoid hard and sticky foods, as well as chewing gum.
It's normal for your mouth to feel sore after you get your braces on. You can take over-the-counter pain medication if needed. To help with the soreness, you can rinse your mouth with a salt water solution (1 teaspoon of salt in 8 ounces of water). Rinse for 30 seconds, then spit it out.
If a wire or bracket comes loose, try to put it back in place with a cotton swab or pencil eraser. If you can't do that, cover the sharp edge with orthodontic wax or silicone putty until you can see your orthodontist.
If you have any questions about how to care for your braces, be sure to ask your orthodontist during your next appointment!