Any time you're at any kind of festival, what's behind your subject of interest becomes important. If your objective is getting a head shot you probably don't have too much to worry about (if you have a long enough lens). Set your F-stop as low as it will go, focus on the eyes and let the background be totally out of focus. If the plan is to get a full length shot (as in today's image) your problems multiply. Even the fastest glass can only do so much. The things that are conspiring against you are your minimum F-stop number (largest aperture), the distance between you and the subject and the distance between the subject and the background. If you look back a couple of posts you'll see a head shot of a friend. He was about half the distance of today's image away, but the background was about two hundred feet behind him. Therefore, the background was fully out of focus. In what started out as today's image, the fellow was probably sixty feet from me, but the people standing in the background were about sixty feet further back. They were definitely not "in focus", but what they were was still recognizable. That gives a good starting point for a montage. To find out about a few of Adobe Photoshop's (PS) extraction tools, hit the "Read More".
The things I don't use are any of the Erase (E) tools. They're all destructive and if you make a mistake there's no going back. I also don't use the Pen (P) tools. There are more modern tools and, if necessary, any selection can be converted to a Path and the Pen tools used to adjust individual points along the Path. I find I can typically tell when someone has stopped learning PS by their dependence on the Pen tool.
On the newer side of things is the Quick Selection Tool (W). It's nested under the Magic Wand Tool (hence the W shortcut key). It's very useful for solid objects with well defined edges, It does tend to leave a slight halo around some cutouts. Using the Modify (Select/Modify) action to either Expand or Contract (depending on if it was easier to select the object or the background) the selection by one (maybe two but almost never three) pixel tightens up the edges and reduces any halos.
If the object being selected has a more textured edge the Refine Edge Tool is available using the Quick Selection Tool. It can be used to define irregular edges. It takes some trial and error at first, but working with it more gives better results. The idea is to learn what parameters work best with differing types of edges.
The Color Range and Focus Range Tools (Select/Color Range or Focus Range) produce good results if there is enough of a difference between either colors (a red ball against a blue sky) or focus (the head shot mentioned above). The few tools in the dialog box help tighten selections.
If the object to be selected has a lot of internal detail (i.e. a tree against the sky) my go to selection device is the Calculations (Edit/Calculations) dialog box. The first step is to go to the Channels Panel and find the Channel with the most contrast. Use that as a basis for using Calculations. You can find many articles that say you have to make a copy of the Channel you're going to use. I find that a little silly. The output after using Calculations is going to be a new Alpha Channel, so the only thing that happens by making a copy of the original Channel is ending up with a extra copy of a Channel that you'll never use. Sort of like a circular argument.
In the Calculations dialog box you can choose which Channels to use, run through all the Blend Modes and find the right combination to produce the best Alpha Channel to use for a Layer Mask. Good stuff.
The last thing to remember is that all Alpha Channels can be tightened up by using the Brush (B) Tool with the Brush Blend Mode (not the Layer Blend Mode) set to Overlay. Since the Alpha Channel is only black and white (no grays), the Brush will only effect total blacks or total whites. It fills in any questionable shades of gray.