What are the most common Selenium mistakes?

Most Selenium pain is self-inflicted rather than a limitation of the tool. The same few anti-patterns appear in almost every unstable suite, and each has a concrete replacement.

Thread.sleep(5000);
driver.findElement(By.xpath("/html/body/div[3]/div[2]/button")).click();

WebDriverWait wait = new WebDriverWait(driver, Duration.ofSeconds(10));
WebElement button = wait.until(ExpectedConditions.elementToBeClickable(
    By.cssSelector("[data-testid='save']")));
button.click();
wait.until(ExpectedConditions.textToBePresentInElementLocated(
    By.cssSelector("[role='status']"), "Saved"));

• Thread.sleep instead of waiting for an observable state
• Absolute XPath and generated class names instead of stable test ids
• A static driver shared across tests, causing state leakage and parallel races
• No quit or cleanup, leaving browser processes and sessions behind
• Implicit and explicit waits mixed, producing unpredictable delays
• Asserting immediately after an action before the UI has updated
• Catching exceptions and retrying inside the test instead of fixing the cause
• Testing every rule through the UI instead of using API or unit tests

The cost compounds. A five-second sleep in twenty tests adds over a minute to every run, and a brittle XPath breaks on a deployment unrelated to the feature. Cleanup failures eventually exhaust CI memory or Grid slots, which then looks like random infrastructure instability.