Every move happens inside a dealing range — from a significant low to a significant high (or vice versa). Draw a Fibonacci from the low to the high and the 50% level is equilibrium: fair value.
The one rule this gives you: buy in discount, sell in premium. You want your longs to start from the cheap half of the range and your shorts from the expensive half. It sounds obvious, but it quietly disqualifies a huge number of bad trades — chasing longs after price has already run into premium is how good analysis becomes a losing trade.
How to set the range. Use the current, relevant swing — the leg you're actually trading within. On a pullback in an uptrend, the range is the impulse leg up; you want to buy the discount of that leg. Getting the range right is a judgment skill that improves with reps, but the discipline it enforces — never buy expensive, never sell cheap — is worth it from day one.