GameObject.Find() / GetComponent<T>()

using UnityEngine;

// Searches for a GameObject by name in the scene (returns null if not found).
GameObject obj = GameObject.Find(string name);

// Searches for a GameObject by tag.
GameObject obj = GameObject.FindWithTag(string tag);

// Gets all GameObjects that match a tag.
GameObject[] objs = GameObject.FindGameObjectsWithTag(string tag);

// Gets a component attached to this GameObject.
T comp = GetComponent<T>();

// Searches this GameObject and its children.
T comp = GetComponentInChildren<T>();

// Searches this GameObject and its parents.
T comp = GetComponentInParent<T>();

// Adds a component to the GameObject.
T comp = gameObject.AddComponent<T>();

A sample combining Inspector assignment, tag-based search, and GetComponent.

FindSample.cs

using UnityEngine;

public class FindSample : MonoBehaviour
{
    // Assigning directly from the Inspector is the most efficient approach.
    [SerializeField] private GameObject player;
    [SerializeField] private Rigidbody2D myRigidbody;

    void Start()
    {
        // Searches for a GameObject by name (use in Start, not Update).
        GameObject enemy = GameObject.Find("Enemy");
        if (enemy != null)
        {
            Debug.Log($"Enemy found: {enemy.transform.position}");
        }

        // FindWithTag() is faster than Find() for tag-based searches.
        GameObject mainCamera = GameObject.FindWithTag("MainCamera");
        if (mainCamera != null)
        {
            Debug.Log($"Main camera: {mainCamera.name}");
        }

        // Gets a component with GetComponent<>().
        Rigidbody rb = GetComponent<Rigidbody>();
        if (rb != null)
        {
            rb.AddForce(Vector3.up * 10f);
        }

        // TryGetComponent combines component retrieval and null check.
        if (TryGetComponent<Animator>(out Animator anim))
        {
            anim.SetTrigger("Jump");
        }

        // Searches children for a component with GetComponentInChildren.
        AudioSource sfx = GetComponentInChildren<AudioSource>();
        if (sfx != null)
        {
            sfx.Play();
        }

        // Gets multiple GameObjects by tag.
        GameObject[] coins = GameObject.FindGameObjectsWithTag("Coin");
        Debug.Log($"Coins: {coins.Length}");
    }
}

Find-family methods scan the entire scene and are expensive. The recommended pattern is to call them once in Awake() or Start() and store the result in a field.

CachedReference.cs

using UnityEngine;

public class CachedReference : MonoBehaviour
{
    // Fields for caching.
    private Rigidbody _rb;
    private Animator _anim;
    private AudioSource _audio;
    private GameObject _uiRoot;

    void Awake()
    {
        // Retrieve and cache components once in Awake().
        _rb = GetComponent<Rigidbody>();
        _anim = GetComponent<Animator>();
        _audio = GetComponentInChildren<AudioSource>();
        _uiRoot = GameObject.FindWithTag("UIRoot"); // Find-family: Awake/Start only
    }

    void Update()
    {
        // NG: Calling GetComponent in Update() scans every frame.
        // GetComponent<Rigidbody>().AddForce(Vector3.up);

        // OK: Use the cached field.
        if (_rb != null)
            _rb.AddForce(Vector3.up * 0.1f);

        if (Input.GetKeyDown(KeyCode.Space) && _anim != null)
            _anim.SetTrigger("Jump");
    }
}

A pattern for adding components at runtime with AddComponent. Useful for effects and temporary behaviors.

DynamicComponent.cs

using UnityEngine;

public class DynamicComponent : MonoBehaviour
{
    void Start()
    {
        // Adds a Rigidbody in code if not already attached.
        if (!TryGetComponent<Rigidbody>(out _))
        {
            Rigidbody rb = gameObject.AddComponent<Rigidbody>();
            rb.mass = 2f;
            rb.useGravity = true;
            Debug.Log("Rigidbody added.");
        }

        // Adds and configures an AudioSource.
        AudioSource audio = gameObject.AddComponent<AudioSource>();
        audio.playOnAwake = false;
        audio.volume = 0.8f;

        // Checks for the presence of a Renderer.
        bool hasRenderer = TryGetComponent<Renderer>(out Renderer rend);
        Debug.Log($"Has Renderer: {hasRenderer}");
        if (hasRenderer)
            Debug.Log($"Material: {rend.material.name}");
    }
}

Common Mistake 1: Using GameObject.Find() Inside Update()

GameObject.Find() scans the entire scene and is expensive. Using it inside Update() causes a significant performance drop every frame.

using UnityEngine;

public class FindInUpdateNG : MonoBehaviour
{
    void Update()
    {
        // NG: Scans the entire scene every frame.
        GameObject enemy = GameObject.Find("Enemy");
        if (enemy != null)
            transform.LookAt(enemy.transform);
    }
}

The corrected version looks like this:

using UnityEngine;

public class FindInUpdateOK : MonoBehaviour
{
    private Transform _enemyTransform; // Cache field

    void Start()
    {
        // OK: Search once during initialization and cache the result.
        GameObject enemy = GameObject.Find("Enemy");
        if (enemy != null)
            _enemyTransform = enemy.transform;
    }

    void Update()
    {
        // Uses the cached reference.
        if (_enemyTransform != null)
            transform.LookAt(_enemyTransform);
    }
}

Common Mistake 2: Accessing GetComponent Return Value Without Null Check

GetComponent returns null when the component is not attached. Accessing it without a null check causes a NullReferenceException.

using UnityEngine;

public class NullCheckNG : MonoBehaviour
{
    void Start()
    {
        // NG: Throws NullReferenceException if Rigidbody is not attached.
        GetComponent<Rigidbody>().AddForce(Vector3.up * 10f);
    }
}

The corrected version looks like this:

using UnityEngine;

public class NullCheckOK : MonoBehaviour
{
    void Start()
    {
        // OK: TryGetComponent combines retrieval and null check in one call.
        if (TryGetComponent<Rigidbody>(out Rigidbody rb))
        {
            rb.AddForce(Vector3.up * 10f);
        }
        else
        {
            Debug.LogWarning("Rigidbody is not attached.");
        }
    }
}

GameObject.Find() scans the entire scene, so calling it inside Update(), which runs every frame, causes a significant performance drop. Call it only once in Start() or Awake() and cache the result in a field. When possible, prefer assigning references directly in the Inspector.

Accessing a null return value from GetComponent<T>() causes a NullReferenceException. Always add a null check, or use TryGetComponent<T>() instead. For debug output, see Debug.Log(). For Unity math functions, see Mathf.