There are lots of different solutions and, depending on your path, you may have a few to choose from. I am using a Poppet to protect but Megan’s link shows alternatives.
Marina’s comment is also one I use. I talk to the house, to my Poppets and meditate on protections and good vibes. Doing it often feels good and can answer your question about knowing it is working. You will feel it.
Here is my grumpy house Poppet. She overlooks my work area and I talk to her regularly. She doesn’t answer back but she is a stoic guard that makes me feel better.
