Here are some best practices for writing clear and efficient IF statements:

Readability:

* Use meaningful variable and condition names: Choose names that clearly describe the purpose of the variable or the condition being evaluated.
* Favor positive conditions: Whenever possible, express conditions in a positive way for better readability. Instead of `if (!isValid)`, write `if (isValid)`.
* Break down complex conditions: If your condition is long and convoluted, consider separating it into smaller, more manageable parts using logical operators (AND, OR) or separate IF statements.

Efficiency:

* Minimize nesting: Deeply nested IF statements can be difficult to follow. Try restructuring your logic to use fewer nested statements or consider alternatives like switch statements for multiple conditions.
* Early return: If a condition at the beginning of your IF block determines the entire outcome, you can return early to avoid unnecessary code execution within the block.
* Consider alternatives: Depending on the situation, other control flow structures like switch statements or dictionary lookups might be more efficient for handling multiple conditions.

Maintainability:

* Use proper indentation: Consistent indentation makes your code visually easier to parse and understand the flow of logic.
* Add comments (when necessary): For complex logic or non-obvious code sections, comments can explain the purpose of the code and improve maintainability.

Here's an example comparing a not-so-clear IF statement with a more readable version:

Not so Clear:

```
if (age >= 18 && !isStudent && !hasDiscountCode) {
price = fullPrice;
} else {
price = discountedPrice;
}
```

Clearer Version:

```
isDiscounted = isStudent || hasDiscountCode;
price = isDiscounted ? discountedPrice : fullPrice;
```

By following these practices, you can write IF statements that are clear, efficient, and easy to maintain for yourself and others working with your code.