First, these are not like the shields you see most of the Wiccans I know that anchor to physical things or points and fill in the lines. Truth be told, those have never hindered me from seeing in or passing though when I am far-seeing or working in other ways. I think you will see why these can be stronger.
First, some basic understanding of who you are is needed. We all form internal barriers to protect ourselves, there are layers, we let some folks know some levels of who we are, others know us deeper, and others even closer. Then there's what is past that which only we see, and past that things we try to hide from ourselves. And then there's what we DO hide from ourselves. There are usually a few layers beyond those too.
The exercise, and yea, it's going to take energy. Find your connection, where ever you can draw from, many of us touch the earth, feeling to flow from our feet, others the air, or other force, what ever works for you, but get calm and in touch with that energy.
Next, close your eyes and breath calmly. Now, look inside, see those layers protecting you, shells within shells, see the outer layer, see the texture, is it smooth, rough, hard or soft, resilient or crystalline? Then, move to the next layer. Same thing, and keep going as deep as you can. When you get to a layer you can't get past, study it. This is a protective shell you have made to protect YOU. Now, see it as a sphere. And take a breath and blow out, as you do see the layer of the sphere enlarge and also stay in place, creating a new layer, this one you can see though as it no longer protects that part you can not see. Breath again and expand it more. Grow it until it expands beyond the inside of you and surrounds you.
Now calmly, drawing on your energy source, keep expanding it until it surrounds what you want to protect, usually your home. let it conform to your space if it hit's someone else's home or appartment.
This takes concentration. A bit of your mind must keep in touch with this to keep it up and in place. With practice you can let it go for a day, then longer and longer and it will stay in place. Practice!!!
To purify the inside, visualize it filling with water, this is your energy, pushing out things that would harm or hinder you. fill it up, you can breath it for this is the energy that sustains you. Once full, you can let the water flow away for the area is clean.
Now, the kind of protections each come with vulnerabilities. If they are hard, they can be cracked, if crystal, shattered, if liquid they can be moved though.
Once you have gotten to the point where you can put up and maintain a shield, you can start to modify it, make it more dynamic. You can make them that just surround you a bit form your skin to go places with you into hostile places.
My personal shield is like a thick gel, it is usually clear, but if something hits it hard it bounces off, someone attacks slow, I can tell and surround the attack or attacker and seal them off from their energy source so they have to use their personal energy and they usually weaken pretty quick.
If you use a mirrored surface, it can reflect attacks well.
And, you can stack them, and with practice, blend them and let them flow so you have many layers with different strengths and weaknesses. If you do this, it is nearly impossible to get though as one if breached, another push them away. Someone has to be very determined to get though it.
Oh, and about making things inside invisible don't let it go too long, beasts that live in the world unseen bounce on it and then wonder what it is, and they start to gather around. It becomes obvious something is there and draws attention. Likewise, sticky shields..
So, I hope that works for folks.