You mean how close to pin it? I use the bent quilters safety pins. You shouldn't be able to lay your hand flat without running into a pin. If you're transporting this quilt you will want to pin pretty closely so it doesn't shift on you. Think about where you're placing the pin in regards to your quilting motif. Don't pin where you're going to quilt. Less removal of pins at awkward times during quilting. I give it to my husband to takes the pins out of when it's finished. He can sit and watch tv and takes pins out.
If you want a better way to make sure it doesn't shift while transporting, use Elmers washable school glue. That's what I mostly use now. Glue everything together and you never have to worry about shifting or removing pins. The sandwich is ready to go.