With shawls specifically, the exact best way to pin them out can vary a bit depending on things like the shawl shape and especially the edging. For example if the edge is supposed to have sharp points on it, you'll want to pin each point in place.

But there are a ton of tutorials and videos and etc around, and if in doubt you can ask for more specific tips here of course! If you're looking at the pattern on Ravelry there are usually even blocking photos included in some of the other projects that get posted so you can see how other people did it.

Main tip is don't worry, it can sound a bit complicated and precarious at first but really it's just a case of wetting the thing then making sure it's in the shape you want it to stay in while it dries.