How to Use GitHub Copilot Without Losing the Plot

Getting signed in

1. 1Update VS Code to the latest release. Copilot's surface changes monthly and stale builds show stale menus.
2. 2Hover the Copilot icon in the Status Bar along the bottom of the window and choose Use AI Features.
3. 3Pick a sign-in method and follow the prompts in your browser. If your employer uses GitHub Enterprise, choose Continue with GHE.com instead.
4. 4With no paid plan you land on Copilot Free, which uses automatic model selection and a fixed monthly allowance.
5. 5Open any code file and type. Grey text ahead of your cursor means it is working.

The keys worth memorizing

1. 1Tab accepts the whole suggestion. It also jumps to and accepts a next edit suggestion elsewhere in the file, which is why an arrow sometimes appears in the gutter.
2. 2Escape dismisses the suggestion and leaves your code untouched.
3. 3Cmd+Right Arrow on macOS, or Ctrl+Right Arrow on Windows and Linux, accepts one word or line at a time. The underrated one.
4. 4Hover the ghost text to see Copilot's alternative suggestions and step between them.
5. 5Cmd+Ctrl+I on macOS or Ctrl+Alt+I on Windows opens the Chat view; Cmd+I or Ctrl+I opens inline chat right at your cursor.
6. 6Shift+Cmd+I on macOS or Ctrl+Shift+I on Windows switches to agents, which edit across multiple files at once.

# weak — Copilot guesses at everything
def parse_date(s):
    

# strong — the contract is stated
def parse_date(s: str) -> datetime | None:
    """Parse an ISO-8601 date string, assuming UTC when no zone is given.

    Returns None for empty or unparseable input.
    Never raises — callers check for None.
    """

The same function, two amounts of context

1. 1Explaining unfamiliar code. Select a block, open inline chat, ask what it does and why, then check the explanation against the code — the fastest way to orient in a codebase you did not write.
2. 2Explaining an error message, stack trace pasted in raw. Often right, and when wrong you find out in seconds by trying the fix.
3. 3Naming and small refactors, which are low-risk because you review the diff regardless.
4. 4Writing tests for code you already understand. Read each test and ask whether it would fail if the code were broken. A surprising number assert things that cannot fail.

What actually goes wrong

1. 1Plausible-but-wrong code: off-by-one errors, inverted conditions, the wrong variable of the right type. GitHub's own docs say suggestions may appear valid without being semantically or syntactically correct.
2. 2Invented API methods. It will confidently call a method that does not exist on that library, because one by that name exists on a similar library. The most common wasted hour.
3. 3Silently outdated patterns. It learned from a great deal of old code, so deprecated APIs and abandoned libraries arrive looking current.
4. 4Insecure defaults: string-concatenated SQL, missing input validation, credentials pasted into source. Nothing in the loop checks for that.
5. 5Suggestions matching public code verbatim. A duplicate-detection filter can block or annotate those, depending on your plan and organization settings.
6. 6The learning trap, which is the expensive one.

1. 1Read every suggestion before pressing Tab. Every one. If that feels slow, the slowness is the real cost of the tool — still cheaper than debugging code nobody understands.
2. 2Delete anything you cannot explain out loud. Not "I think it sorts the list" — what it sorts, in what order, and what it does with an empty list.
3. 3Write your own tests by hand for the first few months. The test is where you state what you meant; outsourcing it outsources the only part that was yours.
4. 4Once a week, switch Copilot off and do one small task from scratch. If that feels impossible you have learned less than you think, and a practice task is a cheap place to find out.

1. 1Close tabs holding secrets, customer data, or anything under NDA before working with Copilot enabled.
2. 2Use content exclusions if you administer the repo or organization — they stop specific paths being used as context at all.
3. 3Check whether your plan uses prompts and suggestions for model training. Individual and business terms differ; the toggle is in your Copilot settings.
4. 4Switch it off for cryptography and authentication, where a plausible-looking mistake is expensive rather than annoying.
5. 5Switch it off while learning a new language's fundamentals. Ghost text finishing your sentences is what stops the syntax sticking.

Symptom, cause, fix

1. 1No ghost text at all. Copilot is disabled for this language or file. Click the Status Bar icon, check the per-language toggle, then look for a repository content exclusion.
2. 2Suggestions are generic and useless. Not enough context. Open the relevant type definitions in tabs and write a signature or contract comment before the cursor.
3. 3It calls a method that does not exist. It pattern-matched a similar library. Open that library's real docs and check the method list — faster than arguing with chat.
4. 4Tab inserts a literal tab. Another extension or snippet is claiming the key. Open Keyboard Shortcuts and search for conflicts on Tab.
5. 5You hit a limit mid-task. Copilot Free has a fixed monthly allowance. Wait for the reset or review the current tiers; the editor keeps working either way.
6. 6Chat ignores your project's conventions. It cannot see conventions you never wrote down. Add a custom instructions file so your standards ride along with every request.
7. 7Agent mode changed more files than expected. You accepted a diff you did not read. Commit before every agent run so one Git command puts you back.

• The Copilot icon in your Status Bar shows active, not slashed.
• You accept with Tab, dismiss with Escape, and take a single word with Cmd or Ctrl plus Right Arrow without thinking.
• You have written a typed signature before the cursor and watched suggestion quality change.
• You have used inline chat to explain a block you did not write, then checked it against the code.
• You can name three specific things Copilot gets wrong.
• You have deleted a suggestion purely because you could not explain it.
• You know what sits in your open tabs while you code, and none of it contains secrets.
• You completed one small task with Copilot off in the last week.