Sit or stand before any fire. Look into the flames (or flame, if using a candle). Visualize the fire bathing you with glowing, protective light. The fire creates a flaming, shimmering sphere around you. If you wish, say the follow or similar words:
Craft the spell in the fire
Craft it well; weave it higher.
Weave it now of shining flame;
None shall come to hurt or maim.
None shall pass this fiery wall;
None shall pass, no none at all.
Repeat this simple yet effective ritual every day when in need.