GitHub Copilot Tips for Effective Suggestions

GitHub Copilot revolutionizes coding by providing AI-powered suggestions directly in your editor. However, many developers accept whatever Copilot offers without realizing they can dramatically improve suggestion quality through better prompting techniques. This guide reveals proven strategies to get more accurate, relevant, and useful code suggestions from Copilot.

I. How Copilot Generates Suggestions

Understanding Copilot's mechanics helps you work with it more effectively.

A. Context Window

• Current file priority: Copilot weights the active file heavily for context.
• Open tabs matter: Other open files inform suggestions—open related code for better results.
• Recent edits: Code you've written recently influences upcoming suggestions.
• Comment context: Comments before code are powerful context signals.

B. What Copilot Can and Cannot Do

• Strengths: Boilerplate code, common patterns, standard implementations, test generation.
• Limitations: Novel algorithms, business-specific logic, code requiring external API knowledge.
• Quality variance: Suggestions range from perfect to completely wrong—always review.

II. Writing Better Comments for Better Suggestions

Comments are your primary tool for communicating intent to Copilot.

A. Descriptive Function Comments

// Bad: Process user
function processUser() { }

// Good: Validate user email format, check against 
// banned domains list, and return sanitized email 
// or throw ValidationError
function validateUserEmail(email: string): string { }

// Copilot now understands exactly what to implement

B. Step-by-Step Comments

• Break down logic: Write comments for each logical step before coding.
• Copilot follows: It generates code matching each commented step.
• Example workflow: Comment "// 1. Fetch user from database", then let Copilot generate the fetch code.

C. Type Hints and Examples

// Input: ["apple", "banana", "cherry"]
// Output: { apple: 5, banana: 6, cherry: 6 }
// Maps each string to its character count
function mapToLengths(strings: string[]): Record<string, number> {
    // Copilot now generates exact implementation
}

III. Essential Keyboard Shortcuts

Master these shortcuts to work efficiently with Copilot suggestions.

A. VS Code Shortcuts

• Tab: Accept current suggestion.
• Esc: Dismiss current suggestion.
• Alt+]: See next alternative suggestion.
• Alt+[: See previous alternative suggestion.
• Ctrl+Enter: Open Copilot panel with multiple suggestions.
• Ctrl+→: Accept next word only (partial acceptance).

B. Using the Suggestions Panel

• Trigger panel: Ctrl+Enter opens panel with up to 10 suggestions.
• Compare options: Review multiple approaches before choosing.
• Different implementations: Often shows varying patterns for the same task.

IV. Context Optimization Strategies

Manage what Copilot "sees" to improve suggestion relevance.

A. Strategic File Opening

• Open related types: When implementing a function, open files with types it uses.
• Open similar implementations: If creating a new service, open existing services for pattern consistency.
• Open test files: When writing code, open existing tests to inform implementation style.

B. Example-Driven Development

• Write examples first: Show Copilot how you want code structured with a manual example.
• Pattern replication: Copilot follows the pattern for subsequent similar functions.
• Consistency benefit: Keeps your codebase uniform.

C. Import Statements

• Add imports early: Import statements tell Copilot which libraries to use.
• Specific imports: Named imports guide toward specific APIs.
• Framework hints: Importing React hooks signals React component context.

V. Function and Variable Naming

Names are critical context signals for Copilot.

A. Descriptive Naming

// Vague: Copilot guesses what to do
function process(data) { }

// Clear: Copilot knows exact intent
function calculateTotalPriceWithDiscounts(cartItems) { }

// Very clear: Includes edge case handling
function calculateTotalPriceWithDiscountsAndTax(
    cartItems, 
    discountCodes, 
    taxRate
) { }

B. Parameter Names

• Self-documenting: Use userId not id, maxRetries not n.
• Type information: Names like userIds: number[] are clearer than ids: any[].
• Default values: timeout = 5000 hints at expected usage.

VI. Breaking Down Complex Tasks

Copilot performs better with smaller, focused functions.

A. Decomposition Strategy

• Single responsibility: One function, one task produces better suggestions.
• Step functions: Create small helper functions rather than one large function.
• Clear boundaries: Copilot understands well-defined inputs and outputs.

B. Workflow Example

// Instead of one massive function:
function processOrder(order) { /* everything */ }

// Break into focused parts:
function validateOrderItems(items) { }
function calculateOrderTotal(items, discounts) { }
function createOrderRecord(validatedItems, total, userId) { }
function sendOrderConfirmation(orderRecord, userEmail) { }

// Copilot generates each with higher accuracy

VII. Test Generation

Copilot excels at generating tests when given proper context.

A. Test File Setup

• Create test file: Name it matching the source file (e.g., utils.test.ts for utils.ts).
• Import source: Import functions you want to test.
• Write first test: Manually write one test as an example.
• Let Copilot continue: It generates similar tests for edge cases.

B. Test Comment Patterns

describe('validateEmail', () => {
    // should return true for valid email format
    // should return false for missing @ symbol
    // should return false for banned domains
    // should handle empty string input
    // should trim whitespace from input
});

VIII. Copilot Chat Integration

Combine inline suggestions with Copilot Chat for complex tasks.

A. When to Use Chat

• Explanations: Ask "What does this code do?" for unfamiliar code.
• Refactoring: Request "Refactor this to use async/await."
• Debugging: Describe bugs and get fix suggestions.
• Documentation: Generate README sections or code comments.

B. Chat Commands

• /explain: Get explanation of selected code.
• /fix: Suggest fixes for broken code.
• /tests: Generate tests for selected code.
• /doc: Generate documentation comments.

IX. Common Pitfalls to Avoid

• Accepting without review: Always verify suggested code works correctly.
• Outdated patterns: Copilot may suggest deprecated APIs—check current docs.
• Security issues: Suggestions may have vulnerabilities—run security scans.
• Over-reliance: Use Copilot to accelerate, not replace understanding.
• Ignoring alternatives: First suggestion isn't always best—check alternatives.

X. Conclusion

GitHub Copilot's effectiveness depends heavily on how you interact with it. By writing descriptive comments, using clear naming conventions, managing file context, and breaking down complex tasks, you can dramatically improve suggestion quality. Remember to always review generated code, use keyboard shortcuts efficiently, and combine inline suggestions with Copilot Chat for best results. The goal is faster development without sacrificing code quality or understanding.

What Copilot tips have improved your workflow? Share your favorite techniques in the comments!