When I am fighting an infection I use a variety of remedies. I may vary it slightly form the stated remedies here depending on the type of infection.
For example I have just had a dental abscess. I treated it with pau d'arco tea, turmeric, cayenne pepper, spirulina, ahwaganda, astragalus, maca, rhodiola plus a whole host of fruit and vegetables. I took capsules of the above herbs several times a day. Within a week I was right as rain. I could eat on the abscessed tooth within 3 to 4 days.
Many herbs aren't designed for long term use and should only be used when you are ill. It's worth knowing which is which for these times. I buy loose herbs and encapsulate myself. This is the cheapest way to buy if you are going to be using herbs regularly as medicine and for preventative means. They can also be made into tinctures or teas in a loose format (which I also do depending on the herb).
Garlic can of course be used but it takes about 4-6 raw cloves of garlic a day to beat an infection. Since I have to be around people, I can't bear to stink that badly! However it's a great option for anyone without access to more exotic herbs. Just remember that a couple of slices of frozen garlic bread is not going to cure your infection! You have to hit it hard. You should also take a probiotic when taking garlic. Odourless capsules are not effective - don't waste your money. Use it in it's fresh state and mainly raw.