To know when to use factoring by grouping, look for polynomials that have four or more terms. Here’s a simple way to do it:

1. Group the Terms: First, split the polynomial into two parts. For example, let’s take $x^3 + x^2 + 2x + 2$. You can group it like this: $(x^3 + x^2) + (2x + 2)$.

2. Factor Each Group: Next, find the common parts in each group and factor them out. From our example, you will get $x^2(x + 1) + 2(x + 1)$.

3. Combine and Factor Out the Common Binomial: Now, look for anything that both groups share. Here, both have a common factor of $(x + 1)$. So, you can write it all together as $(x + 1)(x^2 + 2)$.

You should use this method whenever you see a polynomial that's easy to group!