I hate finishing the quilting, only to discover puckers or even worse, pleats in the finished quilt.
So I pin LOTS, leaving the pins open, then I can remove as I go, and with all those pins while it was stretched out, I rarely ever find puckers or pleats...so start with hand width apart and fill in a bit closer so the top is basted to your point of success...
Experience will teach you that...for me 4" is too far apart.
The other thing, don't pin where you know your major quilting will be. Keep them out of the area where your quilting design is going to make you keep having to stop to remove the pin.
If you have marked your design, that is easier to do than if you just ramble with no design or flow in mind.
You did not say hand or machine (and I have assumed machine for now) or what sort of quilting design you are doing...stitch in the ditch, stipple, filler, grid, etc. And those are also important parts of the issue.
I do both machine quilting for faster projects...and hand quilting for heirloom quality projects. For my hand quilting, I first pin, and then replace the pins with needle & thread basting...
If you PM me, I could use a digital camera of some machine quilted blocks I am just playing around with so you can see...
Oh, one more item. If you are new to this, you need to learn to inspect your pins...not all that got packaged should have passed inspection. You would not want a blunt point to poke a huge hole in your fabric, or one with "wings" on the shaft to cut the threads of your fabric.
Hope there was something here that you found helpful.
Mary Ellen