Here is my method for applying a simple protection spell to pretty much anything. For simplicitie's sake, I'll provide its common usage -- protection of the home.
A star * indicates something that can be substituted or left out.
Step 1. Use any method you feel is necessary to ground, center, cleanse, and ready yourself. This method usually takes quite a bit of energy. It also helps to ready your environment: dim the lights, light candles, etcetera.
Step 2. Choose a spot on the wall for your seal. It does not have to be in any particular spot, but if you feel you should place the seal by a door or window, do so. Begin by channeling your energy through a quartz crystal* or a wand*. Use it to draw a geometric shape on the wall.
~the shape you draw decides how many element locks you will use: triangle-3 square-4 circle-4(the cardinal directions) and so forth~
Step 3. Use sacred oil to dab the corners*. At this point, you can choose to incorporate an incantation. Place the quartz* on the point or corner a lock is to be located. Focus on an element. Channel that one element into the wall at that corner, visualizing a lock. When you have finished, move on to the others. You do not have to use the same element for every lock. Also, it might help to have representations of the elements with you.
Step 4. Once you have completed all the locks for the shape, you may, if you so choose, to add another shape on top of the first one. This makes for a stronger seal. When you are finished, visualize the entire complex of your seal in as much detail as you can. Then, with great intention and will, place your quartz* in the center of it, and when you do, see keys being inserted in every lock you have created. Then, lock the entire seal by turning the whole thing 360 degrees on the wall, and say "lock" "seal" or something else that will put an exclaimation on the process.
Step 5. At this point, the energy of your seal should have spread through out the entire house. Burn incense* to purify the process and any lingering energies. To check and see if you've succeeded, feel around the house for the seal's energy.
After your seal is completed, checking it every day is important. If it starts to weaken, simply empower it with more energy. There is no need to redo the element locks.
I hope you find this useful. If anyone would like to critique or counter my methods, feel free to do so. If you found any success in this, please let me know! I myself have done this several times and found it works very well.