How to get St Augustine grass to grow and thicken up?

Make sure you use pre-emergence applications (gardening store or hardware store) and fertilize according to the pre-emergence instructions. Some use pre-emergence twice a year - fall and just before spring. Talk with your local extension service, they will help. Also, ask the Internet about pre-emergences. Your local gardening store will be more than glad to spend time discussing this in detail.

Augustine likes a lot of water. Be careful using weed killer because technically it is a weed, so make sure the WK used states that it is safe for Augustine. If you have thin areas, just dig plugs from where it is thicker and plug it into bare areas.

I water my runners every day in the summer..throe a little top soil on bare spots