Debug.Log() / Debug.LogError()

using UnityEngine;

// Outputs a normal message in white.
Debug.Log(object message);

// Associates a specific object as the context.
Debug.Log(object message, Object context);

// Outputs a warning message in yellow.
Debug.LogWarning(object message);

// Outputs an error message in red.
Debug.LogError(object message);

// Outputs an error if the condition is false.
Debug.Assert(bool condition, object message);

// Clears the console (editor only).
Debug.ClearDeveloperConsole();

using UnityEngine;

public class DebugSample : MonoBehaviour
{
    // Set the initial health values.
    [SerializeField] private int hp = 100;
    [SerializeField] private int maxHp = 100;

    void Start()
    {
        // Basic log output. String interpolation works here too.
        Debug.Log($"Game start: health = {hp}");

        // Logs object info. Clicking it in the console highlights the object.
        Debug.Log($"This object: {gameObject.name}", this);
    }

    void Update()
    {
        // Logging every frame produces a flood of output, so use conditions to limit it.
        if (Input.GetKeyDown(KeyCode.Space))
        {
            Debug.Log("Space key was pressed.");
        }
    }

    // Method called when taking damage.
    public void TakeDamage(int amount)
    {
        if (amount <= 0)
        {
            // Warn when an unexpected value is received.
            Debug.LogWarning($"Damage amount is 0 or less: {amount}");
            return;
        }

        hp -= amount;
        Debug.Log($"Damage: -{amount} / Remaining health: {hp}");

        if (hp <= 0)
        {
            Debug.LogError("Health reached 0! Check the game over logic.");
        }

        // Use Assert to detect invalid state.
        Debug.Assert(hp <= maxHp, $"Health exceeds max health: {hp} > {maxHp}");
    }
}

In Unity, Debug.Log() outputs only to the editor console, so forgetting to remove it in a production build will not affect game behavior. However, a large number of Debug.Log() calls can impact performance. Keep usage inside Update(), which runs every frame, to a minimum.

To completely strip Debug.Log() calls at build time, wrap them in the #if UNITY_EDITOR preprocessor directive, or set Debug.unityLogger.logEnabled = false in release builds. For finding GameObjects and getting components, see GameObject.Find() / GetComponent<T>().