There are numerous things that can cause vomiting in a dog. The most common problem is eating something they shouldn't, such as getting in the garbage, eating excessive table scraps, eating dead critters outside, etc. Sometimes they chew on sticks, rocks, grass, toys, balls, etc, and this will make them sick also. Sometimes objects they chew on will get lodged in the stomach or intestine and create a blockage. Gastrointestinal viruses (such as parvo, and corona) can also cause vomiting (as well as diarrhea). Intestinal parasites are also a big possibility. Internal problems with the liver , pancreas, or kidneys will also cause dogs to vomit. Pancreatitis is another common problem in dogs (especially Schnauzers!), and results from dogs eating fatty foods/table scraps. Pancreatitis is an inflammation in the pancreas that makes dogs feel very ill and they often vomit profusely. If your dog has a long history of vomiting, there could be a food allergy, or irritable bowel problems. There are many other causes, but those are the most common.
Since it is impossible to determine the cause without an exam and possibly xrays and blood work, you may need to take your dog in to the vet. You can try some pepcid and a bland diet over the weekend, such as boiled boneless/skinless chicken breast and rice mixture (50/50 of each), or boiled ground beef and rice. Feed small amounts every few hours (couple tablespoons). Continue to offer small amounts of water. If she starts to feel better, you can give your dog increasing amounts of food, and add back in the regular kibble after a couple of days. Diarrhea may also accompany vomiting in some cases, and the bland food may help resolve that. You can also give 1 Tbsp of plain yogurt with the bland food to help with any diarrhea. For a miniature schnauzer, I would give 1/4 of a 10 mg Pepcid AC (available in the store, OTC) every 12 hours.
If the pepcid and bland food are of no help, and the vomiting continues, OR if your dog is very lethargic or acts painful, you will need to see your vet. They will need to find the cause of the vomiting and then suggest a treatment plan. If your dog has diarrhea also and it is not resolving, your vet can help you with this as well.
Here is an article which goes over more: http://www.2ndchance.info/vomiting.htm
Let me know if you have further questions. Hope Laney is feeling better soon.